Thread: How is the cursor drawn

  1. 12-09-2001 #1
    Mox
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    How is the cursor drawn

    Hi you all!

    This is a question about the basics of windows. Because I'm trying to make my own GUI (for games) I need to know how they work. It's going well so far, but I always make it harder and harder for myself and now I'm just a bit lost. So to help me back on track: How does windows handle mouse cursor drawing?
    And more in general: Does windows use a backbuffer or something?
    When I draw in windows, I draw to a DC, but what does that do? Has windows got a backbuffer with the whole desktop and windows in (video) memory? So it can erase the mouse cursor and redraw it whenever it moves.

    Well maybe you can explain this a bit, that way I have an idea how to do it myself...
    thanks

    Joren
  2. 12-09-2001 #2
    novacain
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    I think its more like layers but I'm not 100% sure.

    One DC on top of another (z order). The cursor being a small one always on top.

    As to a back buffer, don't you use one?

    I do all my drawing to small DC's. Then when ready the smaller parts are drawn to a desktop sized DC. When I need for the screen to be redrawn this desktop sized DC is BltBit'ed to the screen's DC, another exact copy.
    A paint is now called to redraw just the area I need with InvalidateRect() using the screen's DC.
    These two buffers ensure that I can draw the smaller parts while I redraw the screen. The paint is also fast, one BltBit(), so no wait / freeze while redrawing.
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  3. 12-10-2001 #3
    golem
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    I am almost sure that Windows uses buffer to store part of video memory under the cursor.

    As you might have noticed, no WM_PAINT messages are sent to your window procedure when you move mouse through the window client area, the occupied part of underlying picture renews itself from somewhere. Windows uses black&white pointers.
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