Creating a Nonrectangular Window

Janet Terra
Creating a Nonrectangular Window | Demo 1: Drawing a Nonrectangular Window | Third Part Title Demo 2: Creating a Nonrectangular Window from a Bitmap in Memory

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Creating an irregular shaped window is achieved with WinAPI calls to user32.dll and gdi32.dll. The first step is to create a window without a caption. This can be achieved with the stylebits commands _WS_POPUP in the addbits parameter and _WS_CAPTION in the removebits paramater, or simply using the window_popup style. It is also advisable to keep the window in the forefront. Do this by using the stylebits command _WS_EX_TOPMOST in the extended bits parameter. Remember that any GUI window may be closed with Alt-F4.

For more detailed discussion of stylebits, see Stylebits - Windows .

Demo 1: Drawing a Nonrectangular Window

This first demo draws a circle, a rectangle, and some graphic text. The background is never added to the window. Only the actual drawings, including the graphic text, become part of the window. First, open a captionless window.

 Nomainwin 
 
 'Define the Window 
 WindowWidth = 500 
 WindowHeight = 500 
 UpperLeftX = int((DisplayWidth-WindowWidth)/2) 
 UpperLeftY = int((DisplayHeight-WindowHeight)/2) 
 graphicbox #ShapeWindow.gb, 0, 0, 500, 500 
 stylebits #ShapeWindow.gb, 0, _WS_BORDER, 0, 0 
 
 'Keep the Shaped Window in the Forefront 
 stylebits #ShapeWindow, 0, 0, _WS_EX_TOPMOST, 0 
 
 open "Shape Window" for window_popup as #ShapeWindow 
 #ShapeWindow "trapclose [closeShapeWindow]" 

Once the window is opened, handles and device controls to both the window and the graphicbox must be obtained.

 'Obtain the Handles and Device Controls 
 hBw = hWnd(#ShapeWindow) 
 hBgb = hWnd(#ShapeWindow.gb) 
 hDCw = GetDC(hBw) 
 hDCgb = GetDC(hBgb) 
 
 'The Function 
 Function GetDC(hW) 
 Calldll #user32, "GetDC", _ 
 hW as ulong, _ 
 GetDC as ulong 
 End Function 

Now you're ready to draw an image. In this first demo, the image will be drawn using API calls. These are the steps in the [drawShape] gosub.

1: The Destination - Define a region to hold the finished window. Because this region will be built upon, start with all 0's for x, y, width and height.

 'Original values for hRgn is meaningless 
 hRgn = RectRegion(0, 0, 0, 0) 
 
 'The Function 
 Function RectRegion(ulx, uly, width, height) 
 CallDLL #gdi32, "CreateRectRgn", _ 
 ulx as long, _ 
 uly as long, _ 
 width as long, _ 
 height as long, _ 
 RectRegion as ulong 
 End Function 

2: The Circle - Define the x, y, width and height values for the circle. Select a red brush, paint the designated ellipse, delete the brush.

 'hRgn1 = Elliptical Source Region 
 hRgn1 = EllipticRegion(100, 50, 200, 250) 
 'Paint the Ellipse Red 
 brushColor1 = 255 'Red Brush 
 hBrush1 = createBrush(brushColor1) 
 Call SelObject hDCw, hBrush1 
 Call PaintRegion hDCw, hRgn1 
 Call DelObject hBrush1 
 
 'The Functions and Subs 
 Function RectRegion(ulx, uly, width, height) 
 CallDLL #gdi32, "CreateRectRgn", _ 
 ulx as long, _ 
 uly as long, _ 
 width as long, _ 
 height as long, _ 
 RectRegion as ulong 
 End Function 
 
 Function EllipticRegion(ulx, uly, width, height) 
 CallDLL #gdi32, "CreateEllipticRgn", _ 
 ulx as long, _ 
 uly as long, _ 
 width as long, _ 
 height as long, _ 
 EllipticRegion as ulong 
 End Function 
 Function createBrush(brushColor) 
 Calldll #gdi32, "CreateSolidBrush", _ 
 brushColor as long, _ 
 createBrush as ulong 
 End Function 
 
 Sub PaintRegion hDC, hRgn 
 Calldll #gdi32, "PaintRgn", _ 
 hDC as ulong, _ 
 hRgn as ulong, _ 
 null as long 
 End Sub 
 
 Sub DelObject hObject 
 Calldll #gdi32, "DeleteObject",_ 
 hObject as ulong,_ 
 null as long 
 End Sub 
 
 Sub SelObject hDC, hBrush 
 Calldll #gdi32, "SelectObject", _ 
 hDC as ulong, _ 
 hBrush as ulong, _ 
 null as long 
 End Sub 

Use CombineRgn to add this painted region, hRgn1, to the destination region, hRgn.

 'Set hRgn to the Combination of itself and hRgn1 
 newRgn = CombineRgn(hRgn, hRgn, hRgn1, _RGN_OR) 

Now that region hRgn1 is a part of region hRgn, it is no longer needed. Delete that object to free memory.

 'Delete hRgn1 
 Call DelObject hRgn1 

3: The Rectangle - Define the x, y, width and height values for the rectangle. Select a blue brush, paint the designated rectangle, delete the brush.

 'hRgn2 = Rectangular Source Region 
 hRgn2 = RectRegion(150, 75, 300, 200) 
 'Paint the rectangle blue 
 brushColor2 = 255 * 256^2 'Blue Brush 
 hBrush2 = createBrush(brushColor2) 
 Call SelObject hDCw, hBrush2 
 Call PaintRegion hDCw, hRgn2 
 Call DelObject hBrush2 

Once again, use the API Call CombineRgn to add the pixels of the rectangle hRgn2 to the final destination region hRgn.

 'Set hRgn to the Combination of itself and hRgn2 
 newRgn = CombineRgn(hRgn, hRgn, hRgn2, _RGN_OR) 

The hRgn2 rectangle can now be safely deleted to free up space, as it's been added to the shaped window region hRgn.

 'Delete hRgn2 
 Call DelObject hRgn2 

4: The newly built region made up of regions hRgn1 and hRgn2 can now be set as the window.

 'Set hRgn as the Window 
 Call SetWindowRgn hBw, hRgn, 1 
 
 'The Sub 
 Sub SetWindowRgn hWnd, hRgn, redrawMode 
 Calldll #user32, "SetWindowRgn",_ 
 hWnd as ulong,_ 
 hRgn as ulong,_ 
 redrawMode as boolean,_ 
 SetWindowRgn as long 
 End Sub 

The SetBkMode of #gdi32 can be called to achieve a transparent background for text. Text can then become part of the window.

 'Set background to Transparent 
 Call SetBkMode hDCgb, 1 

ReleaseDC is again called to release memory.

 'Release memory 
 Call ReleaseDC hBgb, hDCbg 

Graphics text is accomplished with native Liberty BASIC code.

 'Format Text 
 #ShapeWindow.gb "font Courier_New 14 Bold" 
 #ShapeWindow.gb "color Black; place 120 150" 
 #ShapeWindow.gb "\Alt-F4 to Close" 
 Wait 

Run your program and a shaped window appears. Close the window with Alt-F4 or include a button for closure. The window will stay on top of other windows, but it is possible for the window to lose focus. If this happens, click on the window before pressing Alt-F4.



Click ShapedDemo1.bas for the entire program.

Third Part Title Demo 2: Creating a Nonrectangular Window from a Bitmap in Memory

Text here. 'code here The second demo creates a nonrectangular window from a bitmap in memory. This demo draws the image, but you could just as easily load the bitmap from file using Loadbmp. The stylebits _WS_BORDER is used to remove the graphicsbox border.

 'Define the Window 
 WindowWidth = 250 
 WindowHeight = 250 
 UpperLeftX = int((DisplayWidth-WindowWidth)/2) 
 UpperLeftY = int((DisplayHeight-WindowHeight)/2) 
 
 stylebits #ShapeWindow.gb, 0, _WS_BORDER, 0, 0 
 graphicbox #ShapeWindow.gb, 0, 0, 250, 250 
 stylebits #ShapeWindow, 0, 0, _WS_EX_TOPMOST, 0 
 
 open "Shape Window" for window_Popup as #ShapeWindow 
 #ShapeWindow "trapclose [closeShapeWindow]" 
 
 'Obtain the Handles and Device Controls 
 hBw = hWnd(#ShapeWindow) 
 hBgb = hWnd(#ShapeWindow.gb) 
 hDCw = GetDC(hBw) 
 hDCgb = GetDC(hBgb) 
 
 'Draw the Shape 
 #ShapeWindow.gb, "Down; Fill Black" 
 Gosub [drawShape] 
 
 Wait 

Once again, after the shapes are drawn, the background color is set to transparent before writing the graphic text. A region to hold the contents of the new window is defined.

 'Set region to null 
 hRgn = RectRegion(0, 0, 0, 0) 

The shapes are drawn and text is written.

 'Draw a Rectangle 
 #ShapeWindow.gb "color darkblue; backcolor blue" 
 #ShapeWindow.gb "place 50 200; boxfilled 225 225" 
 
 'Set background to Transparent 
 Call SetBkMode hDCgb, 1 
 'Release memory 
 Call ReleaseDC hBgb, hDCbg 
 
 'Format and write text 
 #ShapeWindow.gb "font Courier_New 16 86 Bold" 
 #ShapeWindow.gb "color darkgreen; place 5 210" 
 #ShapeWindow.gb "\Alt-F4 to Close" 
 #ShapeWindow.gb "flush" 

Each pixel must be now be read. The background color is black, as defined by

 #ShapeWindow.gb, "down; fill black" 

so only NON-black pixels will become part of the new region, hRgn. Using a nested loop, the pixels can be searched across and down.

 'Read each pixel. Add each pixel to hRgn only if 
 'color is NOT black (0) 
 For x = 0 to 250 
 For y = 0 to 250 
 If pixelColor(hDCgb, x, y) <> 0 Then 
 hTempRgn = RectRegion(x, y, x+1, y+1) 
 newRgn = CombineRgn(hRgn, hRgn, hTempRgn, 3) 
 Call DelObject hTempRgn 
 End If 
 Next y 
 Next x 

Each 2x2 block becomes a region. If the upper left corner pixel is not black, then that newly created tiny region (hTempRgn) becomes part of the final region (hRgn). If the upper left corner pixel is black, then it's not.

A word about searching by pixel. Reading pixel by pixel is a slow process. If you run the demo included in the files archive, be sure to allow 30 - 60 seconds before the background disappears. Larger bitmaps will take considerably longer.

Once the newly formed region, hRgn, is complete, that region is set as the window.

 'Set the region as the Window 
 Call SetWindowRgn hBw, hRgn, 1 

As a reminder, API created objects remain in memory until deleted. When closing the window, be sure to release the memory with DelObject.

 [closeShapeWindow] 
 Call DelObject hBw 
 Close #ShapeWindow 
 End 

The complete program, ShapedDemo2.bas, is included.

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Creating a Nonrectangular Window | Demo 1: Drawing a Nonrectangular Window | Third Part Title Demo 2: Creating a Nonrectangular Window from a Bitmap in Memory