Screen Rotation

Article
06/30/2006

Single screen devices support screen rotation. The functionality is built into the GDI in GWES. The desktop and the shell respond to screen rotation. The RFlat sample driver in %_WINCEROOT%\Public\Common\OAK\Drivers\Display\RFlat supports screen rotation, as do the Geode and MediaGx drivers in %_WINCEROOT%\Public\Common\OAK\CSP\i486\Geode\GXvideo. To enable screen rotation, link with GPERotate.lib and EmulRotate.lib. The entry point is RGPEFlat.

Note If you use the /D switch to specify the display mode with LoadCEPC.exe, you cannot use the DDI_FLAT driver.

For the VGA flat driver, the RGPEFlat class is derived from the GPERotate class, and RGPEFlatSurf is derived from the GPESurfRotate class.

The following table shows the display driver functions for the RGPEFlat class.

Function	Description
NumModes	Called from DrvGetModes, it returns 1.
SetMode	Called from DrvEnablePDEV and creates a palette based on bpp.
InVBlank	Determines if the CRT is in the middle of a vertical blank when the electron beam is off and traversing from the lower right corner to the upper left. During this interval page flipping, animation can be performed to avoid tearing the image.
SetPalette	Called from DrvSetPalette.
GetModeInfo	Called from DrvGetModes.
SetPointerShape	Called from DrvSetPointerShape and DrvSetPointerShape.
MovePointer	Called from DrvMovePointer calls this function, DrvSetPointerShape.
WaitForNotBusy	Called from EmulatedBltRotate in the GPERotate class.
IsBusy	Determines if the display controller is busy or whether it is available to take another command.
GetPhysicalVideoMemory	Used by the Direct Draw Hardware Abstraction Layer (DDHAL). When implementing, you should not return a bus address or physical address. You should return the virtual address of video memory, an address that the CPU can dereference.
Line	Called from DrvStrokePath.
BltPrepare	Called from DrvFillpath DrvAnyBlt.
BltComplete	Called from DrvFillpath DrvAnyBlt.
GetGraphicsCaps	Called from DrvEnablePDEV.
DrvEscape	Responds to rotation request messages DRVESC_GETSCREENROTATION and DRVESC_SETSCREENROTATION.
WrappedEmulatedLine	Wrapper function around the emulated line drawing function.
CursorOn	Turns on the hardware cursor.
CursorOff	Turns off the hardware cursor.
GetRotateModeFromReg	Called from RGPEFlat constructor, and is used to read the registry to get the initial rotation angle.
SetRotateParams	Called from RGPEFlat constructor to set up the screen width and height based on the current rotation angle.
DynRotate	Rotates the screen when DrvEscape gets a DRVESC_SETSCREENROTATION message.

The following shows the functions in the GPESurfRotate class.

Function	Description
SetRotation	Called in the display driver whenever the display angle has changed. The driver calls this function to reset some member variables in the GPESurfaceRotate instance.
RotatePathData	This is a helper function in GPESurfaceRotate used in DrvStrokePath. It rotates the coordinates of the PATHOBJ structure so the lines can be drawn as not rotated.
RotatePathdataBack	This is a helper function in GPESurfaceRotate used in DrvStrokePath. This restores the PATHOBJ data after drawing the lines.
RotateRectl	This is a helper function in GPESurfaceRotate. It is called during a physical drawing and the rectangle needs to be in the real physical orientation.
RotateRectlBack	This is a helper function in GPESurfaceRotate. It restores the rectangle coordinates after drawing.
GetPtr	This is a helper function in GPESurfaceRotate. It passes the pixel coordinates based on the screen the user views, and it returns a pointer to the corresponding place in video memory.

The following table shows the members in the GPERotate class, which is derived from the GPE class.

Member	Description
m_iRotate	The current rotation angle.
m_nScreenWidthSave	The physical screen width when the screen is not rotated. It is used to calculate the coordinate transformation.
m_nScreenHeightSave	The physical screen height. It is used to calculate the coordinate transformation.
RotateRectl	Helper function in GPERotate to perform rectangle coordinate transformation.
RotateRectlBack	Helper function in GPERotate. It restores the rectangle coordinates.
EmulatedBltRotate	This function is called from BltPrepare and blits in place of EmulatedBlt when the screen is rotated.

Screen Rotation

See Also

Additional resources