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> Its traditional to clears the window before showing anything on Win32. Clearing the window happens so fast that you shouldn't see a flicker That is not due t

> Its traditional to clears the window before showing anything on Win32. Clearing the window happens so fast that you shouldn't see a flicker That is not due to speed but due to Windows API being smart with clipping regions/rectangles to only allow pixel updates in damaged regions (e.g. uncovered parts of a window as you move it). Note that nowadays this only happens inside windows as toplevel windows are composed via DWM in an offscreen buffer. Windows also tries to doublebuffer window drawing updates to avoid flickering. However in Win7 (with DWM -aka Aero mode- disabled) and earlier you'd be able to see flickering by, e.g. resizing windows with complex UIs. Also the "tradition" here isn't to clear the window but to invalidate the regions that were damaged so that the next update (which does clear the window) only affects the damaged regions instead of the entire window. This was most common during the 90s and early 2000s though, at some point computers and memory were fast and big enough to do double buffering during paint events (which in some cases you still need to do when working with GDI) to avoid visible flickering - and nowadays most common flickering issues are solved by Windows themselves doing it via composition. > even as the mouse moves over your window (each pixel your mouse cursor moves, Win32API will clear the window to its background, redraw the window (erasing the old mouse pointer), and draw the mouse pointer in the new location. This is what Windows did until Windows 3.1 (and you could see the cursor flickering when, e.g. a control drew itself while the cursor was over it) but with Windows 95 the system composed the mouse cursor to avoid that flickering. However nowadays (and for a long time now actually) the mouse cursor is drawn by the GPU as a separate hardware plane on top of the screen contents. All Windows do in that case is to send the cursor image to the GPU and set the registers that specify the plane (cursor) position whenever the mouse moves - no drawing takes place.

dragontamer 4y ago
> All Windows do in that case is to send the cursor image to the GPU and set the registers that specify the plane (cursor) position whenever the mouse moves - no drawing takes place. On the contrary. The modern GPU has so many buffers that its constantly recalculating every pixel with custom code pixel shaders (transparency and everything) every frame, maybe 60 FPS or faster. Yeah, the CPU doesn't do any of that bit-blit stuff anymore. But the GPU does that constantly every frame, over-and-over again to compose modern windows. VRAM is 500GBps for a reason on modern GPUs. In either case, "blanking" the screen and redrawing it is a fundamentally fast operation 30 years ago, let alone today. Today's computers are so much faster that there are layers of custom-programmable parts running on 2 different processors (CPU passing data to GPU over PCIe) every frame. 4GB+ VRAM buffers on the GPU allows the GPU to save off some work of course, but there's an incredible amount of calculations that occur on every pixel of every frame 60 times a second today. -------- In any case, a pure-text, maybe ASCII (or Unicode) window shouldn't be having these issues.
- badsectoracula 4y ago
  > On the contrary. [..] Yeah, the CPU doesn't do any of that bit-blit stuff anymore. But the GPU does that constantly every frame, over-and-over again to compose modern windows. I was referring to the CPU side obviously since the operation you described in the message i replied to was done on the CPU at the time. Also that plane i refer to is drawn at a later stage to composition - in fact it is used by older Windows versions (before 8) when DWM was disabled (or didn't exist, in WinXP) for the cursor, while the rest of the system did the region-based clipping approach. FWIW it is also used by Xorg nowadays for the exact same reason - and like with Windows without DWM, Xorg without a compositor still uses a region-based clipping approach to drawing but the dedicated plane for mouse cursors to display the cursor.

dragontamer 4y ago

> All Windows do in that case is to send the cursor image to the GPU and set the registers that specify the plane (cursor) position whenever the mouse moves - no drawing takes place. On the contrary. The modern GPU has so many buffers that its constantly recalculating every pixel with custom code pixel shaders (transparency and everything) every frame, maybe 60 FPS or faster. Yeah, the CPU doesn't do any of that bit-blit stuff anymore. But the GPU does that constantly every frame, over-and-over again to compose modern windows. VRAM is 500GBps for a reason on modern GPUs. In either case, "blanking" the screen and redrawing it is a fundamentally fast operation 30 years ago, let alone today. Today's computers are so much faster that there are layers of custom-programmable parts running on 2 different processors (CPU passing data to GPU over PCIe) every frame. 4GB+ VRAM buffers on the GPU allows the GPU to save off some work of course, but there's an incredible amount of calculations that occur on every pixel of every frame 60 times a second today. -------- In any case, a pure-text, maybe ASCII (or Unicode) window shouldn't be having these issues.

badsectoracula 4y ago
> On the contrary. [..] Yeah, the CPU doesn't do any of that bit-blit stuff anymore. But the GPU does that constantly every frame, over-and-over again to compose modern windows. I was referring to the CPU side obviously since the operation you described in the message i replied to was done on the CPU at the time. Also that plane i refer to is drawn at a later stage to composition - in fact it is used by older Windows versions (before 8) when DWM was disabled (or didn't exist, in WinXP) for the cursor, while the rest of the system did the region-based clipping approach. FWIW it is also used by Xorg nowadays for the exact same reason - and like with Windows without DWM, Xorg without a compositor still uses a region-based clipping approach to drawing but the dedicated plane for mouse cursors to display the cursor.