docs/drm-howto /modeset.c modeset_draw(): Not expected display Gradient color but Fixed color ?

[Crazy86321475]

The compiler executes on the virtual machine (vmware ubuntu 18.04), but only the first color is displayed and no more changes .

[dvdhrm]

Can you elaborate?

[liacat]

same case in my environment(vmware ubuntu 22.04).
i found that i must call drmModeSetCrtc very frame， dont know why.

[dimitry-ishenko]

@dvdhrm what they are saying—and what I am also observing on the real hardware (not VM)—is that the framebuffer only gets scanned out once, when you call drmModeSetCrtc(). After that changes made to the framebuffer do not get scanned out and are not displayed on the screen.

Not sure if there was an API change since you wrote these examples, but as suggested in the related issue #7, you have to call drmModeDirtyFB() for the changes to be scanned out.