Tutorial 5: More about Text
Download the example file here.
RGB_value struct
unused db 0
blue db ?
green db ?
red db ?
RGB_value ends
Note that the first byte is not used and should be zero. The order of the remaining three bytes is reversed,ie. blue, green, red. However, we will not use this structure since it's cumbersome to initialize and use. We will create a macro instead. The macro will receive three parameters: red, green and blue values. It'll produce the desired 32-bit RGB value and store it in eax. The macro is as follows:
RGB macro red,green,blue
xor eax,eax
mov ah,blue
shl eax,8
mov ah,green
mov al,red
endm
You can put this macro in the include file for future use.
You can "create" a font by calling CreateFont or CreateFontIndirect. The difference
between the two functions is that CreateFontIndirect receives only one parameter:
a pointer to a logical font structure, LOGFONT. CreateFontIndirect is the more
flexible of the two especially if your programs need to change fonts frequently.
However, in our example, we will "create" only one font for demonstration, we
can get away with CreateFont. After the call to CreateFont, it will return a
handle to a font which you must select into the device context. After that,
every text API function will use the font we have selected into the device context.
WinMain proto :DWORD,:DWORD,:DWORD,:DWORD
include \masm32\include\windows.inc
include \masm32\include\user32.inc
include \masm32\include\kernel32.inc
include \masm32\include\gdi32.inc
includelib \masm32\lib\user32.lib
includelib \masm32\lib\kernel32.lib
includelib \masm32\lib\gdi32.lib
RGB macro red,green,blue
xor eax,eax
mov ah,blue
shl eax,8
mov ah,green
mov al,red
endm
.data
ClassName db "SimpleWinClass",0
AppName db "Our First Window",0
TestString db "Win32 assembly is great and easy!",0
FontName db "script",0
.data?
hInstance HINSTANCE ?
CommandLine LPSTR ?
.code
start:
invoke GetModuleHandle, NULL
mov hInstance,eax
invoke GetCommandLine
mov CommandLine,eax
invoke WinMain, hInstance,NULL,CommandLine, SW_SHOWDEFAULT
invoke ExitProcess,eax
WinMain proc hInst:HINSTANCE,hPrevInst:HINSTANCE,CmdLine:LPSTR,CmdShow:DWORD
LOCAL wc:WNDCLASSEX
LOCAL msg:MSG
LOCAL hwnd:HWND
mov wc.cbSize,SIZEOF WNDCLASSEX
mov wc.style, CS_HREDRAW or CS_VREDRAW
mov wc.lpfnWndProc, OFFSET WndProc
mov wc.cbClsExtra,NULL
mov wc.cbWndExtra,NULL
push hInst
pop wc.hInstance
mov wc.hbrBackground,COLOR_WINDOW+1
mov wc.lpszMenuName,NULL
mov wc.lpszClassName,OFFSET ClassName
invoke LoadIcon,NULL,IDI_APPLICATION
mov wc.hIcon,eax
mov wc.hIconSm,eax
invoke LoadCursor,NULL,IDC_ARROW
mov wc.hCursor,eax
invoke RegisterClassEx, addr wc
invoke CreateWindowEx,NULL,ADDR ClassName,ADDR AppName,\
WS_OVERLAPPEDWINDOW,CW_USEDEFAULT,\
CW_USEDEFAULT,CW_USEDEFAULT,CW_USEDEFAULT,NULL,NULL,\
hInst,NULL
mov hwnd,eax
invoke ShowWindow, hwnd,SW_SHOWNORMAL
invoke UpdateWindow, hwnd
.WHILE TRUE
invoke GetMessage, ADDR msg,NULL,0,0
.BREAK .IF (!eax)
invoke TranslateMessage, ADDR msg
invoke DispatchMessage, ADDR msg
.ENDW
mov eax,msg.wParam
ret
WinMain endp
WndProc proc hWnd:HWND, uMsg:UINT, wParam:WPARAM, lParam:LPARAM
LOCAL hdc:HDC
LOCAL ps:PAINTSTRUCT
LOCAL hfont:HFONT
.IF uMsg==WM_DESTROY
invoke PostQuitMessage,NULL
.ELSEIF uMsg==WM_PAINT
invoke BeginPaint,hWnd, ADDR ps
mov hdc,eax
invoke CreateFont,24,16,0,0,400,0,0,0,OEM_CHARSET,\
OUT_DEFAULT_PRECIS,CLIP_DEFAULT_PRECIS,\
DEFAULT_QUALITY,DEFAULT_PITCH or FF_SCRIPT,\
ADDR FontName
invoke SelectObject, hdc, eax
mov hfont,eax
RGB 200,200,50
invoke SetTextColor,hdc,eax
RGB 0,0,255
invoke SetBkColor,hdc,eax
invoke TextOut,hdc,0,0,ADDR TestString,SIZEOF
TestString
invoke SelectObject,hdc, hfont
invoke EndPaint,hWnd, ADDR ps
.ELSE
invoke DefWindowProc,hWnd,uMsg,wParam,lParam
ret
.ENDIF
xor eax,eax
ret
WndProc endp
end start
CreateFont creates a logical font that is the closest match to the given parameters and the font data available. This function has more parameters than any other function in Windows. It returns a handle to logical font to be used by SelectObject function. We will examine its parameters in detail.
CreateFont proto nHeight:DWORD,\
nWidth:DWORD,\
nEscapement:DWORD,\
nOrientation:DWORD,\
nWeight:DWORD,\
cItalic:DWORD,\
cUnderline:DWORD,\
cStrikeOut:DWORD,\
cCharSet:DWORD,\
cOutputPrecision:DWORD,\
cClipPrecision:DWORD,\
cQuality:DWORD,\
cPitchAndFamily:DWORD,\
lpFacename:DWORD
nHeight The desired height of the characters . 0 means use
default size.
nWidth The desired width of the characters. Normally this
value should be 0 which allows Windows to match the width to the height. However,
in our example, the default width makes the characters hard to read, so I use
the width of 16 instead.
nEscapement Specifies the orientation of the next character
output relative to the previous one in tenths of a degree. Normally, set to
0. Set to 900 to have all the characters go upward from the first character,
1800 to write backwards, or 2700 to write each character from the top down.
nOrientation Specifies how much the character should be rotated
when output in tenths of a degree. Set to 900 to have all the characters lying
on their backs, 1800 for upside-down writing, etc.
nWeight Sets the line thickness of each character. Windows
defines the following sizes:
The description above is by no means comprehensive. You should refer to your Win32 API reference for more details.
invoke SelectObject, hdc, eax
mov hfont,eax
After we get the handle to the logical font, we must use it to select the font into the device context by calling SelectObject. SelectObject puts the new GDI objects such as pens, brushs, and fonts into the device context to be used by GDI functions. It returns the handle to the replaced object which we should save for future SelectObject call. After SelectObject call, any text output function will use the font we just selected into the device context.
RGB 200,200,50
invoke SetTextColor,hdc,eax
RGB 0,0,255
invoke SetBkColor,hdc,eax
Use RGB macro to create a 32-bit RGB value to be used by SetColorText and SetBkColor.
invoke TextOut,hdc,0,0,ADDR TestString,SIZEOF TestString
Call TextOut function to draw the text on the client area. The text will be in the font and color we specified previously.
invoke SelectObject,hdc, hfont
When we are through with the font, we should restore the old font back into
the device context. You should always restore the object that you replaced in
the device context.