Forum > Windows
WinAPI - examples - post 8
440bx:
This post includes examples for a number of API functions and how they can be used to prevent/eliminate flicker. This is the second and last post related to preventing/eliminating flicker. Some of the examples are not directly about flicker, they are included because they are used in other examples that are about reverting/eliminating flicker.
The examples are:
WinAPI - ExtTextOut (ExtTextOut in folder Ex1)
WinAPI - CopyRect
WinAPI - Rectangle
WinAPI - WM_GETMINMAXINFO
WinAPI - ExtTextOut (ExtTextOut in folder Ex2)
WinAPI - GetDC
WinAPI - ReleaseDC
WinAPI - OffsetRect
WinAPI - CopyRect
WinAPI - InflateRect
WinAPI - InvalidateRect
WinAPI - HeapAlloc
WinAPI - GetCursorPos
WinAPI - WindowFromPoint
WinAPI - IsWindow
WinAPI - UpdateWindow
WinAPI - SetBkColor
WinAPI - InvalidateRect (in InvalidateRect)
WinAPI - GetWindowRect
WinAPI - OffsetRect
WinAPI - GetDC
WinAPI - GetDCEx
WinAPI - SetROP2
WinAPI - Rectangle
WinAPI - ReleaseDC
WinAPI - SetRectEmpty
WinAPI - HeapAlloc
WinAPI - CreatePen
WinAPI - PostMessage
WinAPI - SendMessage
WinAPI - SetCapture
WinAPI - ReleaseCapture
WinAPI - SetWindowPos
WinAPI - LockWindowUpdate
WinAPI - UpdateWindow
WinAPI - GetCursorPos
WinAPI - IsWindow
WinAPI - GetParent
WinAPI - WindowFromPoint
WinAPI - UpdateWindow
WinAPI - GetCharacterPlacement (GetCharacterPlacement in folder Ex1)
WinAPI - ExtTextOut
WinAPI - RtlZeroMemory
WinAPI - GetCharacterPlacement (GetCharacterPlacement in folder Ex2)
WinAPI - ExtTextOut
WinAPI - RtlZeroMemory
WinAPI - BitBlt (in BitBlt)
WinAPI - LoadBitmap
WinAPI - CreateCompatibleDC
WinAPI - GetObject
WinAPI - DeleteDC
WinAPI - StretchBlt (in StretchBlt)
WinAPI - LoadBitmap
WinAPI - CreateCompatibleDC
WinAPI - GetObject
WinAPI - DeleteDC
WinAPI - CreateCompatibleBitmap(in CreateCompatibleBitmap)
WinAPI - CreateCompatibleDC
WinAPI - DeleteDC
WinAPI - CreateFont
WinAPI - MoveWindow
WinAPI - GetSysColor
WinAPI - BitBlt
WinAPI - SelectClipRgn (in SelectClipRgn)
WinAPI - CreateFont
WinAPI - GetDC
WinAPI - ReleaseDC
WinAPI - BeginPath
WinAPI - EndPath
WinAPI - PathToRegion
WinAPI - GetRgnBox
WinAPI - OffsetRgn
WinAPI - ExtSelectClipRgn
WinAPI - SelectClipRgn
WinAPI - CallWindowProc (in ColorMixer)
WinAPI - CopyRect
WinAPI - CreateSolidBrush
WinAPI - CreateRectRgnIndirect
WinAPI - ExtSelectClipRgn
WinAPI - SelectClipRgn
WinAPI - ExtTextOut
WinAPI - FrameRect
WinAPI - GetWindowLongPtr
WinAPI - InvalidateRect
WinAPI - MoveWindow
WinAPI - Rectangle
WinAPI - SetFocus
WinAPI - SetScrollInfo
WinAPI - SetScrollPos
WinAPI - SetTextColor
WinAPI - TextOut
WinAPI - WM_CTLCOLORSCROLLBAR
WinAPI - WM_GETMINMAXINFO
WinAPI - WM_VSCROLL
Continued on next post...
440bx:
Continued from previous post ...
WinAPI - ExtTextOut (example 1 of 2)
This first example of the ExtTextOut API is similar to the FlickerMin example in post 7 (see post 7 for the source.)
It demonstrates ExtTextOut's ability to clip text to a rectangle. It clears the background areas as necessary when processing the WM_PAINT message instead of letting the default window procedure clear it when processing the WM_ERASEBKGND. It produces less flicker than FlickerMin because it uses a smaller font. (NOTE: the flicker is easier to see when resizing the window horizontally only.)
Also note that it does not specify CS_HREDRAW nor CS_VREDRAW in the class styles, instead it invalidates the client area, _without erasing it_ when processing the WM_SIZE message.
The rectangle coordinates used to erase the background can be output onto a console by recompiling the program with the "DEBUG" define active. This is useful to see/verify the coordinates of the background rectangles that are erased when painting.
Use the options under the "ExtTextOut" menu to control the clipping of text.
It also demonstrates how to process the WM_GETMINMAXINFO to control the minimum width and height of the window.
WinAPI - InvalidateRect
Carefully controlling which parts of the client area are invalidated can significantly reduce flicker.
This example shows the effect of invalidating the entire client area compared to the effect of invalidating a smaller area that is the one that needs to be updated. When "Invalidate entire area" is selected in the "InvalidateRect" menu, the amount of flicker will be very noticeable. When "Invalidate coordinate area" is selected, the amount of flicker is drastically reduced and confined to a much smaller area.
The flicker left is due to the use of TextOut and specifying TRUE in the call to InvalidateRect when processing the WM_MOUSEMOVE message:
--- Code: Pascal [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} --- InvalidateRect(Wnd, @UpdateRect, TRUE);This causes the coordinate area to be erased thus showing a clear background before TextOut outputs the new coordinate values.
NOTE: All the coordinates shown are relative to the _client area_ of the respective windows.
WinAPI - ExtTextOut (example 2 of 2)
This example is the InvalidateRect example but with all flicker removed. The absence of flicker is due to the different way the coordinate rectangle is invalidated when processing the WM_MOUSEMOVE message:
--- Code: Pascal [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} --- InvalidateRect(Wnd, @CoordinateRect, FALSE); { NO background erase! } Note, that InvalidateRect is instructed not to require the background to be erased by specifying FALSE (third parameter.) This combined with the fact that ExtTextOut repaints the background and the text in one operation eliminates all flicker in the coordinates area.
However, it is still possible to see some occasional flicker when first pressing the left mouse button. The default processing of the WM_LBUTTONDOWN message Invalidates the entire client area with the statement:
--- Code: Pascal [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} --- InvalidateRect(Wnd, nil, TRUE);This will cause some flicker to be noticeable if the left mouse button is very quickly pressed down and released (about 7 to 10 times per seconds) for a few seconds (5 seconds should normally enough.)
That occasional flicker can be removed by selecting "Exclude bottom line from invalidated area" which will cause the call to InvalidateRect to be:
--- Code: Pascal [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} --- MenuItemState := GetMenuState(GetMenu(Wnd), IDM_EXCLUDE, MF_BYCOMMAND); case MenuItemState <> 0 of true : begin { menu item is checked, exclude the bottom of the client area } GetClientRect(Wnd, ClientRect); ClientRect.Bottom := ClientRect.Bottom - Exclude; InvalidateRect(Wnd, @ClientRect, TRUE); end;thus excluding the area where the ExtTextOut definition is drawn causing all flicker to be eliminated.
NOTE: the ExtTextOut attachment contains both examples.
Continued on next post ...
440bx:
Continued from previous post ...
WinAPI - GetCharacterPlacement (example 1 of 2)
ExtTextOut is a powerful function and when it is combined with GetCharacterPlacement its power surfaces.
GetCharacterPlacement has a large number of options and the two examples presented here do not do it justice but, will give a _small_ taste of what it enables ExtTextOut to do. For all the available options, please see MSDN.
This example simply takes a string and uses GetCharacterPlacement to determine how to "spread" it over a specified number of pixels. GetCharacterPlacement returns an array of inter-character distances that are used by ExtTextOut to display the string.
WinAPI - GetCharacterPlacement (example 2 of 2)
The first example above is a bit deceiving. The same example using a slightly different criteria allows converting a proportionally spaced font into a fixed space font. Normally, such a conversion is undesirable because the additional inter-character whitespace is unsightly but, there are exceptions and, this example shows one of them.
One such case is when outputting the value of registers in a debugger. Most fixed fonts have digits that are not particularly easy to read whereas proportional fonts usually have aesthetically pleasing and easy to read digits.
This example turns any hex number consisting of digits 0-F from proportional to fixed and, for comparison, outputs them as they would in their proportional state on the right hand side and their fixed state on the left hand side.
NOTE: the GetCharacterPlacement attachment contains both examples.
Continued on next post ...
440bx:
Continued from previous post ...
WinAPI - BitBlt
Likely the most common method to eliminate flicker is to paint on a bitmap then bitblt the fully drawn bitmap onto the client area. This removes all flicker.
This example is the simplest example of BitBlt-ing meant to serve as a pre-amble to a more sophisticated example that uses it to remove flicker.
Note that this example does NOT use CS_HREDRAW nor CS_VREDRAW and that it uses a NULL_BRUSH as the background color, making it unnecessary to process the WM_ERASEBKGND to tell Windows the program erased the background when it actually didn't. Windows will erase the background with a NULL_BRUSH which does no erasing at all.
WinAPI - StretchBlt
StretchBlt is included in this set of examples only because it is very closely related to BitBlt. Since they are close cousins and it is immoral to break a family, they have been kept together as they should be.
Continued on next post ...
440bx:
Continued from previous post ...
WinAPI - CreateCompatibleBitmap
This example demonstrates double buffering. The top part of the window is drawn with TextOut (and optionally ExtTextOut by re-compiling - see source) thus causing flicker while, the bottom part of the window is first drawn on a bitmap then BitBlt-ed onto the bottom half of the window. The result is that the bottom part of the window is totally flicker free.
To really appreciate the difference, resize the window. When resizing, the top part of the window will flicker significantly while the bottom part won't flicker at all.
WinAPI - SelectClipRgn
This example demonstrates how to use regions to eliminate flicker. Note that it does NOT use double buffering, only regions.
It creates a region that is excluded from the "paintable" region when drawing the background gradient. After the background gradient has been painted then that region is made the "paintable" region and a different gradient is painted in it.
The inclusion and exclusion of the region is controlled by the options under the "Flicker" menu. When the region is excluded, there will be no flicker and, when it is included, flicker will be noticeable when resizing the window.
Continued on next post ...
Navigation
[0] Message Index
[#] Next page