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Alyce
Feb 13, 2012
**GDI Pens and Brushes** [[toc|flat]] //Some text below is copied from the Microsoft Developers Network Library.// For an eBook or printed book on using the API with Liberty BASIC, see: [[http://alycesrestaurant.com/apilb/index.htm|APIs for Liberty BASIC]] =Native Graphic Colors= Liberty BASIC's **color** statement causes graphics to be drawn in with a pen of the specified color. Liberty BASIC's **backcolor** statement causes graphics ojects to be filled with a brush of the specified color. Windows GDI creates colored pens with **CreatePen**. GDI creates brushes with **CreateSolidBrush** and **CreateHashBrush**. =GDI Brushes and Pens in Liberty BASIC= Pens and brushes can be created with GDI commands, then selected into the Device Context of a graphicbox. (See earlier lessons in this series for more on Device Contexts.) Liberty BASIC will use these pens and brushes when drawing objects such as "box", "boxfilled", "circle", "circlefilled" and so on. =CreatePen= Pens are the equivalent of Liberty BASIC's graphics "color" statement. When a pen is selected into a Device Context it is used to draw the outlines of objects, such as circles, lines, etc. Only one pen may be selected into a Device Context at a time. The selected pen is used for all drawing until another pen is selected. The default pen in a Device Context is a solid, black pen that is one pixel in width. **CreatePen** has three input parameters. You must specify a style, a width and a color. All styles other than a solid pen must be one pixel wide. If a different width is specified, the pen style defaults to solid. The pen styles are as follows: || _PS_SOLID || The pen is solid. Width MUST be one. || || _PS_DASH || The pen is dashed. Width MUST be one. || || _PS_DASHDOT || The pen is dotted. Width MUST be one. || || _PS_DASHDOT || The pen has alternating dashes and dots. Width MUST be one. || || _PS_DASHDOTDOT ||The pen has alternating dashes and double dots. Width MUST be one. || || _PS_NULL || The pen is invisible. || The color value is a long integer created from the desired red, green and blue values. See [[DeviceContext|GDI and the Device Context]] for more on long color values. [[code format="lb"]] calldll #gdi32,"CreatePen",_ style as long,_ 'pen style width as long,_ 'width in pixels rgbCol as long,_ 'long color value CreatePen as ulong 'handle to pen end function [[code]] =SelectObject= The pen is not used until it is selected into the Device Context with **SelectObject**. The function returns the handle of the original object of the type and this default object can be selected back into the Device Context later. [[code format="lb"]] CallDLL #gdi32,"SelectObject",_ hDC as uLong,_ 'handle of DC hObj as uLong,_ 'handle of object to select SelectObject as uLong 'returns previously selected object [[code]] =DeleteObject= When an object is no longer needed, we use DeleteObject to free the memory consumed by the object. Do not attempt to delete an object that is currently selected into a Device Context. We first use **SelectObject** to select the default object back into the Device Context. We may then delete the created object, like so: [[code format="lb"]] CallDLL #gdi32,"DeleteObject",_ hObj as uLong,_ 'handle of object r As Boolean [[code]] =CreateSolidBrush= A solid brush is created with this code, which requires a long color value and returns the handle of the solid brush: [[code format="lb"]] calldll #gdi32, "CreateSolidBrush",_ rgbCol as long,_ 'long color value CreateSolidBrush as ulong 'returns handle of brush [[code]] Only one brush may be selected into a Device Context at one time. We do this with **SelectObject*** just as we did for the created pen discussed earlier. We reserve the handle of the default brush to select back into the Device Context later, just as we did for the pen. =CreateHatchBrush= A hatch brush is not a solid color; it has a cross-hatched pattern. The styles may be any of the following. || _HS_BDIAGONAL || 45-degree upward left-to-right hatch || || _HS_CROSS || Horizontal and vertical crosshatch || || _HS_DIAGCROSS || 45-degree crosshatch || || _HS_FDIAGONAL || 45-degree downward left-to-right hatch || || _HS_HORIZONTAL || Horizontal hatch || || _HS_VERTICAL || Vertical hatch || **CreateHatchBrush** also requires a long color value for the brush. [[code format="lb"]] calldll #gdi32, "CreateHatchBrush",_ style as long,_ 'brush style rgbCol as long,_ 'long color value CreateHatchBrush as ulong 'handle of brush [[code]] Once created, it may be selected into a Device Context in exactly the same way as the pen and solid brush discussed earlier. Like them, it must be deleted when no longer needed, in order to free memory. =GDI Drawn Objects= The examples here demonstrate the creation of pens and brushes and their use with native Liberty BASIC drawing commands. We can also draw graphics with GDI commands, using these pens and brushes. We can even draw on memory Device Contexts. This will be covered in a later lesson. =Demo= Run the code and you will see this: [[image:penbrush.jpg]] [[code format="lb"]] nomainwin winWide=700:winHigh=500 WindowWidth=winWide+50:WindowHeight=winHigh+50 UpperLeftX=1:UpperLeftY=1 graphicbox #1.g, 0,0,winWide,winHigh open "GDI Demo" for window as #1 #1 "trapclose [quit]" #1.g "down" hDC = GetDC(hwnd(#1.g)) 'device context handle of graphicbox hPen = CreatePen(_PS_DASHDOT,1,MakeRGB(240,200,140)) oldPen = SelectObject(hDC,hPen) #1.g "place 10 10; box 200 100" hBrush = CreateSolidBrush(MakeRGB(100,200,255)) oldBrush = SelectObject(hDC,hBrush) #1.g "place 10 120; boxfilled 200 250" hHatch = CreateHatchBrush(_HS_CROSS,MakeRGB(200,80,170)) hObj = SelectObject(hDC,hHatch) #1.g "place 10 270; boxfilled 200 420" wait [quit] re = SelectObject(hDC,oldPen) re = SelectObject(hDC,oldBrush) call ReleaseDC hwnd(#1.g),hDC call DeleteObject hPen close #1:end function CreateSolidBrush(rgbCol) calldll #gdi32, "CreateSolidBrush",_ rgbCol as long,_ 'long color value CreateSolidBrush as ulong 'returns handle of brush end function function CreateHatchBrush(style,rgbCol) '_HS_BDIAGONAL 45-degree upward left-to-right hatch '_HS_CROSS Horizontal and vertical crosshatch '_HS_DIAGCROSS 45-degree crosshatch '_HS_FDIAGONAL 45-degree downward left-to-right hatch '_HS_HORIZONTAL Horizontal hatch '_HS_VERTICAL Vertical hatch calldll #gdi32, "CreateHatchBrush",_ style as long,_ 'brush style rgbCol as long,_ 'long color value CreateHatchBrush as ulong 'handle of brush end function function CreatePen(style,width,rgbCol) 'styles '_PS_SOLID The pen is solid. '_PS_DASH The pen is dashed. Width MUST be one. '_PS_DOT The pen is dotted. Width MUST be one. '_PS_DASHDOT The pen has alternating dashes and dots. Width MUST be one. '_PS_DASHDOTDOT The pen has alternating dashes and double dots. Width MUST be one. '_PS_NULL The pen is invisible. 'If width is >1 a solid pen is created. calldll #gdi32,"CreatePen",_ style as long,_ 'pen style width as long,_ 'width in pixels rgbCol as long,_ 'long color value CreatePen as ulong 'handle to pen end function function MakeRGB(red,green,blue) if red<0 then red=0 if red>255 then red=255 if green<0 then green=0 if green>255 then green=255 if blue<0 then blue=0 if blue>255 then blue=255 MakeRGB=(blue*256*256)+(green*256)+red end function function GetDC(h) 'get device context for window: calldll #user32, "GetDC",_ h as ulong,_ 'graphicbox handle GetDC as ulong 'returns handle to device context end function function SelectObject(hDC, hObj) CallDLL #gdi32,"SelectObject",_ hDC as uLong,_ 'handle of DC hObj as uLong,_ 'handle of object to select SelectObject as uLong 'returns previously selected object end function sub DeleteObject hObj CallDLL #gdi32,"DeleteObject",_ hObj as uLong,_ r As Boolean end sub sub ReleaseDC h, hdc calldll #user32, "ReleaseDC",_ h as ulong,_ 'window handle hdc as ulong,_ 'device context ret as long end sub [[code]] ---- [[GDI|GDI Tutorials Home]]