"Clear Display Buffer" is not working

[gm-bug-reporter]

Description

In Room Settings, the option "Clear Display Buffer" is meant to clear the display in areas of the window not covered by viewports by filling them with the window color. However, it currently doesn't do anything. The "Clear Viewport Background" option on Viewports and Cameras seems to do what the "Clear Display Buffer" does instead, even for regions outside of viewports.

Steps To Reproduce

Create a room with a viewport that is either smaller than the window, or that is offset, such that it leaves an empty space. Then disable "Clear Viewport Background" in Viewports and Cameras. If you have any room transition into it, there will be visual remains from the previous scene projected into the empty space, regardless of whether "Clear Display Buffer" is checked.

Which version of GameMaker are you reporting this issue for?

IDE v2024.6.2.162 Runtime v2024.6.1.208

Which operating system(s) are you seeing the problem on?

Windows 10.0.19045.0

Which platform(s) are you seeing the problem on?

GX.games, Windows

7a278f9a-0bb6-41ba-b172-de0dcfdd6d1f

[jackerley]

I've removed the option from the IDE as its use was removed from the runner due to finding a lot of projects having this set unnecessarily.

[YYBartT]

The clear of the display buffer is effectively happening in the provided test project but the application surface is drawn over it (with an alpha of 1). If you add a call to application_surface_draw_enable(false) in obj_persistent_manager's Create event and then draw the application surface manually in that object's Post-Draw event with an alpha value < 1 the display buffer colour will come through:

draw_set_alpha(.5);
draw_surface(application_surface, 0, 0);
draw_set_alpha(1);

The artefacts from the title screen show up on the application surface and remain there because it's never cleared (only parts of it are overwritten by the view's contents because the viewport is offset along x by 292 pixels), unless Clear Viewport Background is checked.

The manual already appears to have all information on clearing the display buffer, mostly on the Room Properties and Draw Events pages.