Screen Rotation
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
/Dswitch 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 DrvFillpathDrvAnyBlt. |
| BltComplete | Called from DrvFillpathDrvAnyBlt. |
| 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. |
See Also
Display Driver Registry Settings | Display Driver Escape Codes | Display Driver Architecture | Display Driver Extensions | Display Driver Samples | Loadcepc.exe Boot Loader Usage | How to Implement Screen Rotation
Last updated on Tuesday, May 18, 2004
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