General DC operations
[GDI functions]

Defines

Typedefs

Functions

Detailed Description

DC means Device Context, just like Graphics Context (GC) of X Lib. DC represents a rectangle area on the actual screen or a virtual screen created in memory. We call the rectangle area as "surface" of the DC.

You can call a GDI function and pass a DC to the function to draw lines, circles, or text. Commonly, you should call a function like GetClientDC or CreateCompatibleDC to get or create a DC, then call GDI functions to draw objects, e.g. MoveTo and LineTo. After finishing drawing, you should call ReleaseDC or DeleteMemDC function to release or destroy the DC.

MiniGUI reserved an global DC called HDC_SCREEN. You can use this DC directly without getting/creating or releasing/destroying.

For main windows or controls, MiniGUI will send a MSG_PAINT message to the window when the whole or part of window area have been invalidated. You should call BegainPaint function to get the DC, then repaint the window, and call EndPaint function to release the DC at the last.

Example:

case MSG_PAINT:
{
    HDC hdc;

    hdc = BeginPaint (hWnd);

    // Draw a line.
    MoveTo (hdc, 0, 0);
    LineTo (hdc, 100, 100);

    EndPaint (hWnd, hdc);
    return 0;
}

Define Documentation

#define CreateCompatibleDC ( hdc   )     CreateCompatibleDCEx(hdc, 0, 0)

Creates a memory DC which is compatible with a given DC.

This function creates a memory DC fully compatible with the reference DC hdc, including pixel format and geomatry.

Parameters:
hdc The reference DC.
Returns:
The handle to the memory DC, HDC_INVALID indicates an error.
See also:
CreateCompatibleDCEx, DeleteMemDC

Definition at line 1616 of file gdi.h.

#define DeleteCompatibleDC ( hdc   )     DeleteMemDC(hdc)

Deletes a memory DC.

This function deletes a memory DC created by CreateCompatibleDC.

Parameters:
hdc The device context to be deleted.
See also:
CreateCompatibleDC, DeleteMemDC

Definition at line 1628 of file gdi.h.

#define HDC_INVALID   0xFFFFFFFF

Indicates an invalid handle to device context.

Definition at line 1105 of file gdi.h.

#define HDC_SCREEN   0

Handle to the device context of the whole screen.

This DC is a special one. MiniGUI uses it to draw popup menus and other global objects. You can also use this DC to draw lines or text on the screen directly, and there is no need to get or release it.

If you do not want to create any main window, but you want to draw on the screen, you can use this DC.

Note:
MiniGUI does not do any clipping operation for this DC, so use this DC may make a mess of other windows.

Definition at line 1093 of file gdi.h.

Typedef Documentation

typedef void(* CB_DIRECT_DRAW_RECT)(HDC hdc, Uint8 *pixels, int pitch, int bytesPerPixel, const RECT *rc, void *context)

Type of directly access pixels hook function.

This function is invoked by LockDCEx, application should implement this function in which could directly read and write the pixels in a DC.

Parameters:
hdc the device context.
pixels the pixels addr point to the rc's left-top in DC.
pitch (the bytes of one scan line) of the DC.
bytesPerPixel bytes per pixel.
rc the rectangle to draw, the field left of which is mapped to pixels.
context the context provided by application.

Definition at line 1686 of file gdi.h.

typedef int(* ON_UPDATE_SECONDARYDC)(HWND hwnd, HDC secondary_dc, HDC real_dc, const RECT *secondary_rc, const RECT *real_rc, const RECT *main_update_rc)

The callback type of on updating secondary DC.

Parameters:
hwnd The handle to the updated window.
secondary_dc The update src dc.
real_dc The update dst dc.
secondary_rc The rectangle relative to secondary_dc.
real_rc The rectangle relative to real_dc.
main_update_dc The rectangle relative to main window.
Returns:
The update result.

Definition at line 1871 of file gdi.h.

Function Documentation

BOOL GUIAPI ConvertMemDC ( HDC  mem_dc,
HDC  ref_dc,
DWORD  flags 
)

Converts a memory DC to have a same format as a reference DC.

This function converts a memory DC mem_dc in order to let it have the same pixel format as the reference DC ref_dc. This function will try to create a new surface for mem_dc, and then copies and maps the surface of ref_dc to it so the blit of the converted memory DC will be as fast as possible.

The flags parameter has the same semantics as CreateMemDC. You can also pass MEMDC_FLAG_RLEACCEL in the flags parameter and MiniGUI will try to RLE accelerate colorkey and alpha blits in the resulting memory DC.

Parameters:
mem_dc The device context to be converted.
ref_dc The reference device context.
flags The memory DC flags, has the same semantics as CreateMemDC.
Returns:
TRUE on success, otherwise FALSE.
See also:
CreateMemDC, DeleteMemDC
HDC GUIAPI CreateCompatibleDCEx ( HDC  hdc,
int  width,
int  height 
)

Creates a memory DC which is compatible with the specified reference DC.

This function creates a memory DC which have the same pixel format as the specified reference DC hdc. The same pixel format means that the memory DC will have the same pixel depth, the same RGB composition, or the same palette as the reference DC. Note that the memdc will have the same DC attributes as the reference DC.

Parameters:
hdc The handle to the reference DC.
width The expected width of the result memory DC. If it is zero, the width will be equal to the width of the reference DC.
height The expected height of the result memory DC. If it is zero, the height will be equal to the height of the reference DC.
Returns:
The handle to the memory DC, HDC_INVALID indicates an error.
See also:
CreateCompatibleDC
HDC GUIAPI CreateMemDC ( int  width,
int  height,
int  depth,
DWORD  flags,
Uint32  Rmask,
Uint32  Gmask,
Uint32  Bmask,
Uint32  Amask 
) [inline, static]

Creates a memory DC.

This function creates a memory DC which have the specified flags and pixel format.

Parameters:
width The expected width of the result memory DC.
height The expected height of the result memory DC.
depth The expected color depth of the memory DC.
flags The memory DC flags, can be or'ed values of the following flags:
  • MEMDC_FLAG_SWSURFACE
    Creates the surface of memory DC in the system memory.
  • MEMDC_FLAG_HWSURFACE
    Creates the surface of memory DC in the video memory.
  • MEMDC_FLAG_SRCCOLORKEY
    The created memory DC will use a source color key to blit to other DC.
  • MEMDC_FLAG_SRCALPHA
    The created memory DC will use a source alpha blending to blit to other DC.
  • MEMDC_FLAG_RLEACCEL
    The memory DC will be RLE encoded.
Parameters:
Rmask The bit-masks of the red components in a pixel value.
Gmask The bit-masks of the green components in a pixel value.
Bmask The bit-masks of the blue components in a pixel value.
Amask The bit-masks of the alpha components in a pixel value.
Returns:
The handle to the memory DC, HDC_INVALID indicates an error.
See also:
CreateMemDCEx, CreateMemDCFromBitmap, CreateMemDCFromMyBitmap, CreateCompatibleDCEx

Definition at line 1434 of file gdi.h.

References CreateMemDCEx(), and NULL.

HDC GUIAPI CreateMemDCEx ( int  width,
int  height,
int  depth,
DWORD  flags,
Uint32  Rmask,
Uint32  Gmask,
Uint32  Bmask,
Uint32  Amask,
void *  bits,
int  pitch 
)

Creates a memory DC.

This function creates a memory DC which have the specified flags and pixel format, and uses the pre-allocated buffer as the surface if bits is not NULL.

Parameters:
width The expected width of the result memory DC.
height The expected height of the result memory DC.
depth The expected color depth of the memory DC.
flags The memory DC flags, can be or'ed values of the following flags:
  • MEMDC_FLAG_SWSURFACE
    Creates the surface of memory DC in the system memory.
  • MEMDC_FLAG_HWSURFACE
    Creates the surface of memory DC in the video memory.
  • MEMDC_FLAG_SRCCOLORKEY
    The created memory DC will use a source color key to blit to other DC.
  • MEMDC_FLAG_SRCALPHA
    The created memory DC will use a source alpha blending to blit to other DC.
  • MEMDC_FLAG_RLEACCEL
    The memory DC will be RLE encoded.
Parameters:
Rmask The bit-masks of the red components in a pixel value.
Gmask The bit-masks of the green components in a pixel value.
Bmask The bit-masks of the blue components in a pixel value.
Amask The bit-masks of the alpha components in a pixel value.
bits The pointer to the pre-allocated surface. If this is NULL, MiniGUI will try to allocate the surface from video memory or system memory.
pitch The pitch (the number of bytes of one scan line) of the surface.
Returns:
The handle to the memory DC, HDC_INVALID indicates an error.
Note:
If you pass a pre-allocated surface buffer to this function, MiniGUI will not free the buffer when you delete the memdc by calling DeleteMemDC.
See also:
CreateMemDC, CreateMemDCFromBitmap, CreateMemDCFromMyBitmap, CreateCompatibleDCEx

Referenced by CreateMemDC().

HDC GUIAPI CreateMemDCFromBitmap ( HDC  hdc,
const BITMAP *  bmp 
)

Creates a memory DC from a reference DC and a BITMAP object.

This function creates a memory DC compatible with the specified DC, and use the bits of the BITMAP object as the surface of the memory DC. The created memory DC will have the same geometry as the BITMAP object.

Parameters:
hdc The reference DC.
bmp The BITMAP object.
Returns:
The handle to the memory DC, HDC_INVALID indicates an error.
See also:
CreateMemDCFromMyBitmap, DeleteMemDC, BITMAP
HDC GUIAPI CreateMemDCFromMyBitmap ( const MYBITMAP *  my_bmp,
const RGB *  pal 
)

Creates a memory DC from a device independent MYBITMAP object.

This function creates a memory DC which have the same pixel format as the MYBITMAP object my_bmp, and use the bits of the MYBITMAP object as the surface of the memory DC. The created memory DC will have the same geometry as the MYBITMAP object. If the depth of my_bmp is 8-bit, the function will use pal to initialize the palette of the memory DC.

Note that the color depth of a memory DC can not be less than 8. Thefore, if the color depth of the MYBITMAP object is less than 8, this function will return HDC_INVALID.

Note that if the MYBITMAP object has the flag MYBMP_FLOW_UP, this function will return HDC_INVALID as well.

Parameters:
my_bmp The device independent MYBITMAP object.
pal The palette of the MYBITMAP object. If the depth of my_bmp is larger than 8-bit, this argument can be NULL.
Returns:
The handle to the memory DC, HDC_INVALID indicates an error.
See also:
CreateMemDCFromBitmap, DeleteMemDC, MYBITMAP
HDC GUIAPI CreatePrivateClientDC ( HWND  hwnd  ) 

Creates a private client DC of a window.

This function creates a private client DC of the window hwnd and returns the handle to the DC.

When you calling CreatePrivateClientDC function to create a private client DC, MiniGUI will create the DC in the system heap, rather than allocate one from the DC pool. Thus, you can keep up the DC in the life cycle of the window, and are not needed to release it for using by other windows.

Parameters:
hwnd The handle to the window.
Returns:
The handle to the DC, HDC_INVALID indicates an error.
See also:
DeletePrivateDC
HDC GUIAPI CreatePrivateDC ( HWND  hwnd  ) 

Creates a private window DC of a window.

This function creates a private window DC of the window hwnd and returns the handle to the DC.

When you calling CreatePrivateDC function to create a private DC, MiniGUI will create the DC in the system heap, rather than allocate one from the DC pool. Thus, you can keep up the private DC in the life cycle of the window, and are not needed to release it for using by other windows.

Parameters:
hwnd The handle to the window.
Returns:
The handle to the DC, HDC_INVALID indicates an error.
See also:
DeletePrivateDC
HDC GUIAPI CreatePrivateSubDC ( HDC  hdc,
int  off_x,
int  off_y,
int  width,
int  height 
)

Creates a private SubDC of a window.

This function creates a private SubDC of the DC and returns the handle of the SubDC.

When you calling CreatePrivateSubDC function to create a private Sub DC, MiniGUI will create the DC in the system heap, rather than allocate one from the DC pool. Thus, you can keep up the DC in the life cycle of the window, and are not needed to release it for using by other windows.

Parameters:
hdc The handle of the DC.
off_x The x-coordinate of the sub DC in the parent DC (in device coordinate system).
off_y The y-coordinate of the sub DC in the parent DC (in device coordinate system).
width The expected width of the sub DC.
height The expected height of the sub DC.
Returns:
The handle to SubDC, HDC_INVALID indicates an error.
See also:
DeletePrivateDC
HDC GUIAPI CreateSecondaryDC ( HWND  hwnd  ) 

Creates a secondary window DC of a window.

This function creates a secondary DC for the main window hwnd and returns the handle to the secondary DC.

When you calling CreateSecondaryDC function, MiniGUI will create a memory DC which is compatible with HDC_SCREEN.

When a main window have the extended style WS_EX_AUTOSECONDARYDC, MiniGUI will create a Secondary DC for this main window in the creation progress of the main window, and destroy the DC when you destroy the window. MiniGUI will use this Secondary DC and its sub DCs to render the window content and childen.

Parameters:
hwnd The handle to the window.
Returns:
The handle to the DC, HDC_INVALID indicates an error.
See also:
DeleteSecondaryDC
HDC GUIAPI CreateSubMemDC ( HDC  parent,
int  off_x,
int  off_y,
int  width,
int  height,
BOOL  comp_to_parent 
)

Creates a sub memory DC in the given memory DC.

This function creates a sub memory DC in the given memory DC (the parent memory DC). Note that the new sub memdc will have the same DC attributes as the parent memdc.

Parameters:
parent The handle to the parent memory DC.
off_x The x-coordinate of the sub memory DC in the parent DC (in device coordinate system).
off_y The y-coordinate of the sub memory DC in the parent DC (in device coordinate system).
width The expected width of the sub memory DC.
height The expected height of the sub memory DC.
comp_to_parent The flag indicates whether the sub memdc is compliant to the parent dc.
Returns:
The handle to the memory DC; HDC_INVALID indicates an error.
Note:
Only defined for _USE_NEWGAL.
See also:
CreateMemDC
void GUIAPI DeleteMemDC ( HDC  mem_dc  ) 

Deletes a memory DC.

This function deletes the memory DC mem_dc, and frees the surface of the DC. For the memory DC created from BITMAP object or MYBITMAP object, the bits used by the surface of the DC will be reserved.

Parameters:
mem_dc The device context to be deleted.
See also:
CreateMemDC, CreateMemDCFromBitmap, CreateMemDCFromMyBitmap
void GUIAPI DeletePrivateDC ( HDC  hdc  ) 

Deletes the DC returned by CreatePrivateDC or CreatePrivateClientDC or CreatePrivateSubDC.

Parameters:
hdc The handle to the DC.
See also:
CreatePrivateDC, CreatePrivateClientDC
void GUIAPI DeleteSecondaryDC ( HWND  hwnd  ) 

Deletes the secondary DC of the window.

Parameters:
hwnd The handle to the window.
See also:
CreateSecondaryDC
HDC GUIAPI GetClientDC ( HWND  hwnd  ) 

Gets a client DC of a window.

This function gets a client DC of the specified hwnd, and returns the handle to the DC. MiniGUI will try to return an unused DC from the internal DC pool, rather than allocate a new one from the system heap. Thus, you should release the DC when you finish drawing as soon as possible.

Parameters:
hwnd The handle to the window.
Returns:
The handle to the DC, HDC_INVALID indicates an error.
Note:
You should call ReleaseDC to release the DC when you are done.
See also:
GetDC, ReleaseDC
HDC GUIAPI GetDC ( HWND  hwnd  ) 

Gets a window DC of a window.

This function gets a window DC of the specified hwnd, and returns the handle to the DC. MiniGUI will try to return an unused DC from the internal DC pool, rather than allocate a new one from the system heap. Thus, you should release the DC when you finish drawing as soon as possible.

Parameters:
hwnd The handle to the window.
Returns:
The handle to the DC, HDC_INVALID indicates an error.
Note:
You should call ReleaseDC to release the DC when you are done.
See also:
GetClientDC, ReleaseDC
unsigned int GUIAPI GetGDCapability ( HDC  hdc,
int  iItem 
)

Returns a capability of a DC.

This function returns the capability of the specified item iItem of the DC hdc.

Parameters:
hdc The handle to the DC.
iItem An integer presents the capablity, can be one of the following values:
  • GDCAP_COLORNUM
    Tell GetGDCapability to return the colors number of the DC. Note the for a DC with 32-bit depth, the function will return 0xFFFFFFFF, not 0x100000000.
  • GDCAP_HPIXEL
    Tell GetGCapability to return the horizontal resolution of the DC.
  • GDCAP_VPIXEL
    Tell GetGDCapability to return the vertical resolution of the DC.
  • GDCAP_MAXX
    Tell GetGDCapability to return the maximal visible x value of the DC.
  • GDCAP_MAXY
    Tell GetGDCapability to return the maximal visible y value of the DC.
  • GDCAP_DEPTH
    Tell GetGDCapability to return the color depth of the DC. The returned value can be 1, 4, 8, 15, 16, 24, or 32.
  • GDCAP_BITSPP
    Tell GetGDCapability to return the bits number for storing a pixle in the DC.
  • GDCAP_BPP
    Tell GetGDCapability to return the bytes number for storing a pixle in the DC.
  • GDCAP_RMASK
    Tell GetGDCapability to return the pixel red color mask for the DC.
  • GDCAP_GMASK
    Tell GetGDCapability to return the pixel green color mask for the DC.
  • GDCAP_BMASK
    Tell GetGDCapability to return the pixel blue color mask for the DC.
  • GDCAP_AMASK
    Tell GetGDCapability to return the pixel alpha color mask for the DC.
  • GDCAP_PITCH
    Tell GetGDCapability to return the pitch (the bytes of one scan line) of the DC.
Returns:
The capbility.
HDC GUIAPI GetPrivateClientDC ( HWND  hwnd  ) 

Returns the private client DC of a window.

This function returns the private client DC of the window hwnd which have extended style WS_EX_USEPRIVATECDC.

When a main window have the extended style WS_EX_USEPRIVATECDC, or a control class have the style CS_OWNDC, MiniGUI will create a private client DC for this window in the creation progress of the window, and destroy the DC when you destroy the window, and use this private client DC in default message handlers. So there will be some improvments on drawing/repaint performance. You can alos call this function to get the private client DC, and use it to draw anything in your window.

Parameters:
hwnd The handle to the window.
Returns:
The handle to the private client DC, HDC_INVALID indicates an error.
See also:
CreatePrivateClientDC
HDC GUIAPI GetSecondaryClientDC ( HWND  hwnd  ) 

Retrives and returns the client secondary DC of a specific window.

This function retrives and returns the client secondary DC of the main window hwnd.

When a main window have the secondary DC, MiniGUI will use this secondary DC and its sub DCs to render the content of the window and its children.

Parameters:
hwnd The handle to the main window.
Returns:
The handle to the client secondary DC, HDC_SCREEN indicates that the main window has no secondary DC.
See also:
ReleaseSecondaryDC, SetSecondaryDC
HDC GUIAPI GetSecondaryDC ( HWND  hwnd  ) 

Retrives and returns the secondary DC of a specific window.

This function retrives and returns the secondary DC of the window hwnd.

When a main window have the secondary DC, MiniGUI will use this secondary DC and its sub DCs to render the content of the window and its children.

Parameters:
hwnd The handle to the window.
Returns:
The handle to the secondary DC, HDC_SCREEN indicates that the window has no secondary DC.
See also:
ReleaseSecondaryDC, SetSecondaryDC
HDC GUIAPI GetSubDC ( HDC  hdc,
int  off_x,
int  off_y,
int  width,
int  height 
)

This function gets a sub DC which is compliant to the specified client DC.

This function creates a sub client DC, which is restricted in the specified rectangle and compliant to the specified client DC hdc. Note that you should release the returned dc by calling ReleaseDC.

Parameters:
hdc The handle to the parent client DC.
off_x The x-coordinate of the sub DC in the parent DC (in device coordinate system).
off_y The y-coordinate of the sub DC in the parent DC (in device coordinate system).
width The expected width of the sub DC.
height The expected height of the sub DC.
Returns:
The handle to the new sub DC, HDC_INVALID indicates an error.
Note:
You should call ReleaseDC to release the DC when you are done.
See also:
GetDC, GetClientDC, ReleaseDC
BOOL GUIAPI IsCompatibleDC ( HDC  hdc1,
HDC  hdc2 
)

Check whether a given DC is compliant to a specific DC.

This function checks whether a give DC hdc2 is compliant to the specific DC hdc1.

Parameters:
hdc1 The handle to a DC.
hdc2 The handle to another DC.
Returns:
TRUE when hdc2 is compiliant to hdc1, otherwise FALSE.
See also:
CreateCompatibleDCEx
Uint8 *GUIAPI LockDC ( HDC  hdc,
const RECT *  rw_rc,
int *  width,
int *  height,
int *  pitch 
)

Locks a dc to get direct access to pixels in the DC.

Calling this function will try to lock the DC hdc to directly access the pixels of the DC. You should tell this function the rectangle to be accessed, and the function will return the requested width, height and pitch of the DC. The access beyond requested width and height will be invalid.

Locking a DC which uses screen surface will lock some global objects, such as mouse cursor, and so on. All GDI calls of other threads (in MiniGUI-Threads) or other process (in MiniGUI-Processes) will be blocked as well. So you should call UnlockDC to unlock the DC as soon as possible, and should not call any system function in the duration of locking the DC.

Parameters:
hdc The handle to the device context.
rw_rc The rectangle in device coordinate system to be accessed in the DC.
width The width of the effective rectangle can access will be returned through this pointer.
height The height of the effective rectangle can access will be returned through this pointer.
pitch The pitch of the scan line of the DC will be returned through this pointer. Pitch means the length of the scan line in bytes.
Returns:
The bits pointer to the upper-left corner of the requested rectangle, NULL on error.
See also:
UnlockDC, LockDCEx

Example:

    /*
     * lock the dc and draw the scan line with random color.
     */

    int i, width, height, pitch;
    RECT rc = {0, 0, 200, 200};
    int bpp = GetGDCapability (hdc, GDCAP_BPP);
    Uint8* frame_buffer = LockDC (hdc, &rc, &width, &height, &pitch);
    Uint8* row = frame_buffer;

    for (i = 0; i < *height; i++) {
        memset (row, rand ()%0x100, *width * bpp);
        row += *pitch;
    }

    UnlockDC (hdc);
BOOL GUIAPI LockDCEx ( HDC  hdc,
const PCLIPRGN  region,
void *  context,
CB_DIRECT_DRAW_RECT  cb 
)

directly access the pixels in a DC.

This function fill region by function cb that directly accesses pixels in a DC. This function is used to draw region more effiently. The function that lock __mg_gdilock should not be invoked any more after invoking this function, or else it will cause deadlock. UnlockDC should be invoked after invoking this function that will call back CB_DIRECT_DRAW_RECT, other process could not draw any more until the DC has been unlocked.

Parameters:
hdc the device context.
region the visible region to draw.
context the context provided by application, which is as a parameter of cb.
cb the direct draw function that directly accesses pixels which should be implemented by application. if cb is NULL, the region will be filled by current brush color.
Returns:
if LockDCEx success return TRUE, else return FALSE;
See also:
UnlockDC, LockDC
void GUIAPI ReleaseDC ( HDC  hdc  ) 

Releases a DC from DC pool.

This function releases the DC returned by GetDC or GetClientDC.

Parameters:
hdc The handle to the DC.
See also:
GetDC, GetClientDC, GetSubDC
void GUIAPI ReleaseSecondaryDC ( HWND  hwnd,
HDC  hdc 
)

Release the DC returned by GetSecondaryDC or GetSecondaryClientDC.

Parameters:
hwnd The handle to the window.
hdc The handle to the secondary DC.
Returns:
void
See also:
GetSecondaryDC, GetSecondaryClientDC
BOOL GUIAPI RestoreDC ( HDC  hdc,
int  saved_dc 
)

Restores a device context (DC) to the specified state.

This function restores a device context (DC) to the specified state. The DC is restored by popping state information off a stack created by earlier calls to the SaveDC function.

Parameters:
hdc The handle to the DC.
saved_dc Specifies the saved state to be restored. If this parameter is positive, saved_dc represents a specific instance of the state to be restored. If this parameter is negative, saved_dc represents an instance relative to the current state. For example, -1 restores the most recently saved state.
Returns:
If the function succeeds, the return value is nonzero. If the function fails, the return value is zero.
Note:
The stack can contain the state information for several instances of the DC. If the state specified by the specified parameter is not at the top of the stack, RestoreDC deletes all state information between the top of the stack and the specified instance.
See also:
SaveDC
int GUIAPI SaveDC ( HDC  hdc  ) 

Saves the current state of a device context.

This function saves the current state of the specified device context (DC) by copying data describing selected objects and graphic modes (such as pen, brush, palette, font, pen, region, drawing mode, and mapping mode) to a context stack.

Parameters:
hdc The handle to the DC whose state is to be saved.
Returns:
If the function succeeds, the return value identifies the saved state. If the function fails, the return value is zero.
Note:
This function can be used any number of times to save any number of instances of the DC state. A saved state can be restored by using the RestoreDC function.
See also:
RestoreDC
BOOL GUIAPI SetMemDCAlpha ( HDC  mem_dc,
DWORD  flags,
Uint8  alpha 
)

Sets the alpha value for the entire surface of a DC, as opposed to using the alpha component of each pixel.

This function sets the alpha value for the entire surface of the DC mem_dc, as opposed to using the alpha component of each pixel. This value measures the range of transparency of the surface, 0 being completely transparent to 255 being completely opaque. An alpha value of 255 causes blits to be opaque, the source pixels copied to the destination (the default). Note that per-surface alpha can be combined with colorkey transparency.

If flags is 0, alpha blending is disabled for the surface. If flags is MEMDC_FLAG_SRCALPHA, alpha blending is enabled for the surface. OR'ing the flag with MEMDC_FLAG_RLEACCEL requests RLE acceleration for the surface; if MEMDC_FLAG_RLEACCEL is not specified, the RLE acceleration will be removed. If flags is MEMDC_FLAG_SRCPIXELALPHA, per-pixel alpha blending is enabled for the surface.

Parameters:
mem_dc The device context.
flags The alpha value specific memory DC flags.
alpha the alpha value for the entire surface of the DC mem_dc.
Returns:
TRUE on success, otherwise FALSE.
See also:
SetMemDCColorKey
BOOL GUIAPI SetMemDCColorKey ( HDC  mem_dc,
DWORD  flags,
Uint32  color_key 
)

Sets the color key (transparent pixel) of a memory DC.

This function sets the color key (transparent pixel) of the memory DC mem_dc. If flags is MEMDC_FLAG_SRCCOLORKEY (optionally OR'ed with MEMDC_FLAG_RLEACCEL), color_key will be the transparent pixel in the source DC of a blit. MEMDC_FLAG_RLEACCEL requests RLE acceleration for the source of the DC if present, and removes RLE acceleration if absent. If flags is 0, this function clears any current color key.

Parameters:
mem_dc The device context.
flags The color key specific memory DC flags.
color_key The color_key of the memory DC.
Returns:
TRUE on success, otherwise FALSE.
See also:
SetMemDCAlpha
HDC GUIAPI SetSecondaryDC ( HWND  hwnd,
HDC  secondary_dc,
ON_UPDATE_SECONDARYDC  on_update_secondarydc 
)

Set a window's secondary DC and the callback procedure for the secondary DC update.

This function set the secondary DC of the main window hwnd and returns the handle to the old seconadary DC.

Parameters:
hwnd The handle to the main window.
secondary_dc The secondary DC which will be the new secondary DC of the main window.
on_update_secondarydc The callback procedure for the secondary DC update. You can pass one of two sepcial values:

  • ON_UPDSECDC_DEFAULT
    The default operation to update the secondary DC to the real DC of the main window.
  • ON_UPDSECDC_DONOTHING
    No any operation occures.
Returns:
The handle to the old secondary DC, HDC_SCREEN indicates the main window has no secondary DC before calling this function.
See also:
DeleteSecondaryDC
void GUIAPI UnlockDC ( HDC  hdc  ) 

Unlocks a locked DC.

Parameters:
hdc The locked DC.
See also:
LockDC, LockDCEx
HWND GUIAPI WindowFromDC ( HDC  hdc  ) 

Get the window handle from DC.

This function returns the handle to a window according to the handle to DC of the window.

Parameters:
hdc The handle to the DC.
Note:
Do not call this function on memory DC.
See also:
GetDC.
Generated on Thu Apr 7 15:58:37 2011 for MiniGUI V3.0.12 API Reference by  doxygen 1.6.3