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// 24 february 2014
package ui
import (
// "syscall"
"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
// 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
}
var stdDlgSizes = [nctypes]dlgunits{
c_button: dlgunits{
width: 50,
height: 14,
},
c_checkbox: dlgunits{
// widtdh is not defined here so assume longest
longest: true,
height: 10,
},
c_combobox: dlgunits{
longest: true,
height: 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,
},
}
var (
_getTextMetrics = gdi32.NewProc("GetTextMetricsW")
_getWindowDC = user32.NewProc("GetWindowDC")
_releaseDC = user32.NewProc("ReleaseDC")
)
func (s *sysData) preferredSize() (width int, height int) {
var dc _HANDLE
var tm _TEXTMETRICS
var baseX, baseY int
r1, _, err := _getWindowDC.Call(uintptr(s.hwnd))
if r1 == 0 { // failure
panic(err) // TODO return it instead
}
dc = _HANDLE(r1)
r1, _, err = _getTextMetrics.Call(
uintptr(dc),
uintptr(unsafe.Pointer(&tm)))
if r1 == 0 { // failure
panic(err) // TODO return it instead
}
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(err) // TODO return it instead
}
// 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
}
// attempts to mimic the behavior of kernel32.MulDiv()
// caling it directly would be better (TODO)
// alternatively TODO make sure the rounding is correct
func muldiv(ma int, mb int, div int) int {
xa := int64(ma) * int64(mb)
xa /= int64(div)
return int(xa)
}
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
}
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