Screen Scrolling rendering error, game screen size off by 1 pixel both horizontally and vertically

[drone1400]

First of all, I am talking about the Windows release of DinkHD V2.05

When the Screen Scrolling effect is enabled, during the actual scrolling effect itself, the game-screen area is too big by 1 pixel in both width and height.

This offset error seems to be consistent regardless of resolution. I have tested this at both 640x480 and 1280x960 and noticed the same thing happening.

At 640x480, the game-screen area is 601x401 pixels instead of 600x400.

At 1280x960, the game-screen area is 1201x801 pixels instead of 1200x800.

The extra pixel line, both horizontally and vertically, is just pure black and overrides the right sidebar and the bottom hud elements.

I have uploaded some short video recordings and screenshots that showcase the issue.

NOTE: At 1280x960, when scrolling towards the left, another rendering error can be seen. There is a left-over single pixel width line from one of the sidebars right in between the two game screens. However, I believe this is related to a separate scaling specific rendering issue which I shall be posting about shortly.

640x480 video: https://github.com/user-attachments/assets/54cb6a38-2a5e-458a-83df-d99f1163bcdf
1280x960 video: https://github.com/user-attachments/assets/164f3afa-af41-42b3-b014-16dfe780c29d

Size	Normal	Left	Right	Up	Down
640x480
1280x960

EDIT: tried organizing the screenshots so they take less space xD

[SethRobinson]

Hey, appreciate the detailed info!

I can see the code is adding a bit to fix a seam that pops up when doing screen scrolling:

However, if the screen is exactly 640X480 (or any exact 4:3 ratio?) it doesn't need this fix. (the first versions of DinkHD ran only on the iPhone and required scaling)

So I've added this code which seams (ha) to fix it, but only if smoothing is off and if running at an exact 4:3 ratio like 640X480:

if (fabs((dstRect.GetWidth() / dstRect.GetHeight()) - (4.0f / 3.0f)) < 0.01f)
{
	bNeedSeamFix = false;
}

if (bNeedSeamFix)
{
	//without normal antialiasing we don't need to do much, but this does fix tiny black artifacts during the screen transition
	dstOffset = rtRectf(-0.05, -0.05f, 0.05f, 0.05);
	srcOffset = rtRectf(0.4, 0.4, -0.4, -0.4);
}

Hmm, in both cases there is still a little black line on the right and bottom border that probably shouldn't be there, but is likely caused by something else, it's a lot of weird matrix math that keeps multiple levels of scaling to keep aspect ratio correct on weird screen sizes. (I can't just have a window the correct size, it has to be full screen on mobile devices)

Suspect that's due to something else though.

Anyway thanks, this fix will be in the next build