Why does my Intuition screen not clip height?

[bork]

I'm setting up a custom Intuition screen with a size larger than the required standard lo-res display size, as I want to scroll a little for extra content.

No matter if I declare the SA_Overscan as OSCAN_TEXT or pass a configured clip rect via SA_DClip, the screen does not clip height when scrolling, yet clips width as expected.

Here is the setup code:

	

#define DISPLAY_WIDTH (320)
#define DISPLAY_HEIGHT (256)

#define SCREEN_WIDTH (512)
#define SCREEN_HEIGHT (512)

...

struct Rectangle clipRect = {
	.MinX = 0,
	.MaxX = DISPLAY_WIDTH - 1,
	.MinY = 0,
	.MaxY = DISPLAY_HEIGHT - 1
};

_system.screen = OpenScreenTags(NULL,
	SA_Type, CUSTOMSCREEN,
	SA_Width, SCREEN_WIDTH,
	SA_Height, SCREEN_HEIGHT,
	SA_Depth, DISPLAY_DEPTH,
	SA_Quiet, TRUE,
	SA_ShowTitle, FALSE,
	//SA_Overscan, OSCAN_TEXT,
	SA_DClip, (ULONG)&clipRect,
	TAG_END 
);

Any ideas?

[bork]

For future reference I have found a solution:

Instead of using the OpenScreen function's width and height to describe and allocate a bitmap for the larger screen area, then attempting to use the clip rect to keep it confined to the display area, I instead allocated the screen bitmap via AllocBitmap and passed it to the screen via SA_BitMap tag with width and height set to the display dimensions. This method allows scrolling of the larger screen area in both axes to be correctly clipped.

[tygre]

Hi and thanks!