// 24 february 2014 package ui import ( "fmt" "unsafe" ) // For Windows, Microsoft just hands you a list of preferred control sizes as part of the MSDN documentation and tells you to roll with it. // These sizes are given in "dialog units", which are independent of the font in use. // We need to convert these into standard pixels, which requires we get the device context of the OS window. // References: // - http://msdn.microsoft.com/en-us/library/windows/desktop/aa511279.aspx#controlsizing for control sizes // - http://msdn.microsoft.com/en-us/library/ms645502%28VS.85%29.aspx - the calculation needed // - http://support.microsoft.com/kb/125681 - to get the base X and Y // (thanks to http://stackoverflow.com/questions/58620/default-button-size) // For push buttons, date/time pickers, links (which we don't use), toolbars, and rebars (another type of toolbar), Common Controls version 6 provides convenient methods to use instead, falling back to the old way if it fails. // As we are left with incomplete data, an arbitrary size will be chosen const ( defaultWidth = 100 // 2 * preferred width of buttons ) type dlgunits struct { width int height int longest bool // TODO actually use this getsize uintptr area bool // use area sizes instead } var stdDlgSizes = [nctypes]dlgunits{ c_button: dlgunits{ width: 50, height: 14, getsize: _BCM_GETIDEALSIZE, }, c_checkbox: dlgunits{ // widtdh is not defined here so assume longest longest: true, height: 10, }, c_combobox: dlgunits{ // technically the height of a combobox has to include the drop-down list (this is a historical accident: originally comboboxes weren't drop-down) // but since we're forcing Common Controls version 6, we can take advantage of one of its mechanisms to automatically fix this mistake (bad practice but whatever) // see also: http://blogs.msdn.com/b/oldnewthing/archive/2006/03/10/548537.aspx // note that the Microsoft guidelines pages don't take the list size into account longest: true, height: 12, // from http://msdn.microsoft.com/en-us/library/windows/desktop/bb226818%28v=vs.85%29.aspx; the page linked above says 14 }, c_lineedit: dlgunits{ longest: true, height: 14, }, c_label: dlgunits{ longest: true, height: 8, }, c_listbox: dlgunits{ longest: true, // height is not clearly defined here ("an integral number of items (3 items minimum)") so just use a three-line edit control height: 14 + 10 + 10, }, c_progressbar: dlgunits{ width: 237, // the first reference says 107 also works; TODO decide which to use height: 8, }, c_area: dlgunits{ area: true, }, } var ( _selectObject = gdi32.NewProc("SelectObject") _getDC = user32.NewProc("GetDC") _getTextExtentPoint32 = gdi32.NewProc("GetTextExtentPoint32W") _getTextMetrics = gdi32.NewProc("GetTextMetricsW") _releaseDC = user32.NewProc("ReleaseDC") ) // This function runs on uitask; call the functions directly. func (s *sysData) preferredSize() (width int, height int) { // the preferred size of an Area is its size if stdDlgSizes[s.ctype].area { return s.areawidth, s.areaheight } if msg := stdDlgSizes[s.ctype].getsize; msg != 0 { var size _SIZE r1, _, _ := _sendMessage.Call( uintptr(s.hwnd), msg, uintptr(0), uintptr(unsafe.Pointer(&size))) if r1 != uintptr(_FALSE) { // success return int(size.cx), int(size.cy) } // otherwise the message approach failed, so fall back to the regular approach println("message failed; falling back") } var dc _HANDLE var tm _TEXTMETRICS var baseX, baseY int r1, _, err := _getDC.Call(uintptr(s.hwnd)) if r1 == 0 { // failure panic(fmt.Errorf("error getting DC for preferred size calculations: %v", err)) } dc = _HANDLE(r1) r1, _, err = _selectObject.Call( uintptr(dc), uintptr(controlFont)) if r1 == 0 { // failure panic(fmt.Errorf("error loading control font into device context for preferred size calculation: %v", err)) } r1, _, err = _getTextMetrics.Call( uintptr(dc), uintptr(unsafe.Pointer(&tm))) if r1 == 0 { // failure panic(fmt.Errorf("error getting text metrics for preferred size calculations: %v", err)) } baseX = int(tm.tmAveCharWidth) // TODO not optimal; third reference has better way baseY = int(tm.tmHeight) r1, _, err = _releaseDC.Call( uintptr(s.hwnd), uintptr(dc)) if r1 == 0 { // failure panic(fmt.Errorf("error releasing DC for preferred size calculations: %v", err)) } // now that we have the conversion factors... width = stdDlgSizes[s.ctype].width if width == 0 { width = defaultWidth } height = stdDlgSizes[s.ctype].height width = muldiv(width, baseX, 4) // equivalent to right of rect height = muldiv(height, baseY, 8) // equivalent to bottom of rect return width, height } var ( _mulDiv = kernel32.NewProc("MulDiv") ) func muldiv(ma int, mb int, div int) int { // div will not be 0 in the usages above // we also ignore overflow; that isn't likely to happen for our use case anytime soon r1, _, _ := _mulDiv.Call( uintptr(int32(ma)), uintptr(int32(mb)), uintptr(int32(div))) return int(int32(r1)) } type _SIZE struct { cx int32 // originally LONG cy int32 } type _TEXTMETRICS struct { tmHeight int32 tmAscent int32 tmDescent int32 tmInternalLeading int32 tmExternalLeading int32 tmAveCharWidth int32 tmMaxCharWidth int32 tmWeight int32 tmOverhang int32 tmDigitizedAspectX int32 tmDigitizedAspectY int32 tmFirstChar uint16 tmLastChar uint16 tmDefaultChar uint16 tmBreakChar uint16 tmItalic byte tmUnderlined byte tmStruckOut byte tmPitchAndFamily byte tmCharSet byte }