func (c *Canvas) MeasureText(text string, font *Font, bounds Rectangle, format DrawTextFormat) (boundsMeasured Rectangle, runesFitted int, err error) {
// HACK: We don't want to actually draw on the Canvas here, but if we use
// the DT_CALCRECT flag to avoid drawing, DRAWTEXTPARAMc.UiLengthDrawn will
// not contain a useful value. To work around this, we create an in-memory
// metafile and draw into that instead.
if c.measureTextMetafile == nil {
c.measureTextMetafile, err = NewMetafile(c)
if err != nil {
return
}
}
hFont := win.HGDIOBJ(font.handleForDPI(c.dpiy))
oldHandle := win.SelectObject(c.measureTextMetafile.hdc, hFont)
if oldHandle == 0 {
err = newError("SelectObject failed")
return
}
defer win.SelectObject(c.measureTextMetafile.hdc, oldHandle)
rect := &win.RECT{
int32(bounds.X),
int32(bounds.Y),
int32(bounds.X + bounds.Width),
int32(bounds.Y + bounds.Height),
}
var params win.DRAWTEXTPARAMS
params.CbSize = uint32(unsafe.Sizeof(params))
strPtr := syscall.StringToUTF16Ptr(text)
dtfmt := uint32(format) | win.DT_EDITCONTROL | win.DT_WORDBREAK
height := win.DrawTextEx(
c.measureTextMetafile.hdc, strPtr, -1, rect, dtfmt, ¶ms)
if height == 0 {
err = newError("DrawTextEx failed")
return
}
boundsMeasured = Rectangle{
int(rect.Left),
int(rect.Top),
int(rect.Right - rect.Left),
int(height),
}
runesFitted = int(params.UiLengthDrawn)
return
}
func (c *Canvas) DrawText(text string, font *Font, color Color, bounds Rectangle, format DrawTextFormat) error {
return c.withFontAndTextColor(font, color, func() error {
rect := bounds.toRECT()
ret := win.DrawTextEx(
c.hdc,
syscall.StringToUTF16Ptr(text),
-1,
&rect,
uint32(format)|win.DT_EDITCONTROL,
nil)
if ret == 0 {
return newError("DrawTextEx failed")
}
return nil
})
}