Legacy GM Screen glitching and "Tearing" after resize

My game is at 256x240 resolution, running in Windows 7 in a resizeable window. If I run the game and resize the window, (using the mouse) it will start to 'tear' and white almost polygonal flashes will appear on the screen as im moving my character. At one time, I was in a small room, and it kept flashing like a weird combination of two of the tilesets meshed together for a millisecond or two every 3 to 5 seconds.

What would cause this, is this normal or is it the way i have rooms/drawing/sprites/etc that cause these glitches to happen ; and if so, how do I fix it?


Friendly Tyrant
Forum Staff
Does this only happen when you resize the window? A flash or a glitch on resize is normal as the GPU has to adjust everything. If it's happening after the resize then no it's not normal... Do you have a video or a GIF of the issue? Also, why do you want to make the window resizeable? This complicates matters greatly as you have to make the view ports and cameras adaptive to ANY size and ANY aspect ratio.
It happens AFTER the resizing. Mainly when the screen is scrolling because im moving the player (there is no other moving sprites on screen (usually).

Ill try to cook up a gif/vid in a bit. Im mainly resizing it because im not debugging in full screen / native resolution, and thought it might have those graphical issues when its run how its meant to be.

Is this any indication of my code running too thick - am I running too much code at once?