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canvas.go
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canvas.go
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// Copyright 2010 The Walk Authorc. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// +build windows
package walk
import (
"log"
"syscall"
"unicode/utf8"
"unsafe"
"github.com/lxn/win"
)
// DrawText format flags
type DrawTextFormat uint
const (
TextTop DrawTextFormat = win.DT_TOP
TextLeft DrawTextFormat = win.DT_LEFT
TextCenter DrawTextFormat = win.DT_CENTER
TextRight DrawTextFormat = win.DT_RIGHT
TextVCenter DrawTextFormat = win.DT_VCENTER
TextBottom DrawTextFormat = win.DT_BOTTOM
TextWordbreak DrawTextFormat = win.DT_WORDBREAK
TextSingleLine DrawTextFormat = win.DT_SINGLELINE
TextExpandTabs DrawTextFormat = win.DT_EXPANDTABS
TextTabstop DrawTextFormat = win.DT_TABSTOP
TextNoClip DrawTextFormat = win.DT_NOCLIP
TextExternalLeading DrawTextFormat = win.DT_EXTERNALLEADING
TextCalcRect DrawTextFormat = win.DT_CALCRECT
TextNoPrefix DrawTextFormat = win.DT_NOPREFIX
TextInternal DrawTextFormat = win.DT_INTERNAL
TextEditControl DrawTextFormat = win.DT_EDITCONTROL
TextPathEllipsis DrawTextFormat = win.DT_PATH_ELLIPSIS
TextEndEllipsis DrawTextFormat = win.DT_END_ELLIPSIS
TextModifyString DrawTextFormat = win.DT_MODIFYSTRING
TextRTLReading DrawTextFormat = win.DT_RTLREADING
TextWordEllipsis DrawTextFormat = win.DT_WORD_ELLIPSIS
TextNoFullWidthCharBreak DrawTextFormat = win.DT_NOFULLWIDTHCHARBREAK
TextHidePrefix DrawTextFormat = win.DT_HIDEPREFIX
TextPrefixOnly DrawTextFormat = win.DT_PREFIXONLY
)
var gM *uint16
func init() {
AppendToWalkInit(func() {
gM = syscall.StringToUTF16Ptr("gM")
})
}
type Canvas struct {
hdc win.HDC
hBmpStock win.HBITMAP
window Window
dpi int
bitmap *Bitmap
recordingMetafile *Metafile
measureTextMetafile *Metafile
doNotDispose bool
}
func NewCanvasFromImage(image Image) (*Canvas, error) {
switch img := image.(type) {
case *Bitmap:
hdc := win.CreateCompatibleDC(0)
if hdc == 0 {
return nil, newError("CreateCompatibleDC failed")
}
succeeded := false
defer func() {
if !succeeded {
win.DeleteDC(hdc)
}
}()
var hBmpStock win.HBITMAP
if hBmpStock = win.HBITMAP(win.SelectObject(hdc, win.HGDIOBJ(img.hBmp))); hBmpStock == 0 {
return nil, newError("SelectObject failed")
}
succeeded = true
return (&Canvas{hdc: hdc, hBmpStock: hBmpStock, bitmap: img, dpi: img.dpi}).init()
case *Metafile:
c, err := newCanvasFromHDC(img.hdc)
if err != nil {
return nil, err
}
c.recordingMetafile = img
return c, nil
}
return nil, newError("unsupported image type")
}
func newCanvasFromWindow(window Window) (*Canvas, error) {
hdc := win.GetDC(window.Handle())
if hdc == 0 {
return nil, newError("GetDC failed")
}
return (&Canvas{hdc: hdc, window: window}).init()
}
func newCanvasFromHDC(hdc win.HDC) (*Canvas, error) {
if hdc == 0 {
return nil, newError("invalid hdc")
}
return (&Canvas{hdc: hdc, doNotDispose: true}).init()
}
func (c *Canvas) init() (*Canvas, error) {
if c.dpi == 0 {
c.dpi = dpiForHDC(c.hdc)
}
if win.SetBkMode(c.hdc, win.TRANSPARENT) == 0 {
return nil, newError("SetBkMode failed")
}
switch win.SetStretchBltMode(c.hdc, win.HALFTONE) {
case 0, win.ERROR_INVALID_PARAMETER:
return nil, newError("SetStretchBltMode failed")
}
if !win.SetBrushOrgEx(c.hdc, 0, 0, nil) {
return nil, newError("SetBrushOrgEx failed")
}
return c, nil
}
func (c *Canvas) Dispose() {
if !c.doNotDispose && c.hdc != 0 {
if c.bitmap != nil {
win.SelectObject(c.hdc, win.HGDIOBJ(c.hBmpStock))
win.DeleteDC(c.hdc)
if err := c.bitmap.postProcess(); err != nil {
log.Printf("*Canvas.Dispose - failed to post-process bitmap: %s", err.Error())
}
} else {
win.ReleaseDC(c.window.Handle(), c.hdc)
}
c.hdc = 0
}
if c.recordingMetafile != nil {
c.recordingMetafile.ensureFinished()
c.recordingMetafile = nil
}
if c.measureTextMetafile != nil {
c.measureTextMetafile.Dispose()
c.measureTextMetafile = nil
}
}
func (c *Canvas) DPI() int {
if c.window != nil {
return c.window.DPI()
}
return c.dpi
}
func (c *Canvas) withGdiObj(handle win.HGDIOBJ, f func() error) error {
oldHandle := win.SelectObject(c.hdc, handle)
if oldHandle == 0 {
return newError("SelectObject failed")
}
defer win.SelectObject(c.hdc, oldHandle)
return f()
}
func (c *Canvas) withBrush(brush Brush, f func() error) error {
return c.withGdiObj(win.HGDIOBJ(brush.handle()), f)
}
func (c *Canvas) withFontAndTextColor(font *Font, color Color, f func() error) error {
return c.withGdiObj(win.HGDIOBJ(font.handleForDPI(c.DPI())), func() error {
oldColor := win.SetTextColor(c.hdc, win.COLORREF(color))
if oldColor == win.CLR_INVALID {
return newError("SetTextColor failed")
}
defer func() {
win.SetTextColor(c.hdc, oldColor)
}()
return f()
})
}
func (c *Canvas) HDC() win.HDC {
return c.hdc
}
func (c *Canvas) Bounds() Rectangle {
return RectangleTo96DPI(c.BoundsPixels(), c.DPI())
}
func (c *Canvas) BoundsPixels() Rectangle {
return Rectangle{
Width: int(win.GetDeviceCaps(c.hdc, win.HORZRES)),
Height: int(win.GetDeviceCaps(c.hdc, win.VERTRES)),
}
}
func (c *Canvas) withPen(pen Pen, f func() error) error {
return c.withGdiObj(win.HGDIOBJ(pen.handleForDPI(c.dpi)), f)
}
func (c *Canvas) withBrushAndPen(brush Brush, pen Pen, f func() error) error {
return c.withBrush(brush, func() error {
return c.withPen(pen, f)
})
}
// ellipse draws an ellipse in 1/96" units. sizeCorrection parameter is in native pixels.
//
// Deprecated: Newer applications should use ellipsePixels.
func (c *Canvas) ellipse(brush Brush, pen Pen, bounds Rectangle, sizeCorrection int) error {
return c.ellipsePixels(brush, pen, RectangleFrom96DPI(bounds, c.DPI()), sizeCorrection)
}
// ellipsePixels draws an ellipse in native pixels.
func (c *Canvas) ellipsePixels(brush Brush, pen Pen, bounds Rectangle, sizeCorrection int) error {
return c.withBrushAndPen(brush, pen, func() error {
if !win.Ellipse(
c.hdc,
int32(bounds.X),
int32(bounds.Y),
int32(bounds.X+bounds.Width+sizeCorrection),
int32(bounds.Y+bounds.Height+sizeCorrection)) {
return newError("Ellipse failed")
}
return nil
})
}
// DrawEllipse draws an ellipse in 1/96" units.
//
// Deprecated: Newer applications should use DrawEllipsePixels.
func (c *Canvas) DrawEllipse(pen Pen, bounds Rectangle) error {
return c.ellipse(nullBrushSingleton, pen, bounds, 0)
}
// DrawEllipsePixels draws an ellipse in native pixels.
func (c *Canvas) DrawEllipsePixels(pen Pen, bounds Rectangle) error {
return c.ellipsePixels(nullBrushSingleton, pen, bounds, 0)
}
// FillEllipse draws a filled ellipse in 1/96" units.
//
// Deprecated: Newer applications should use FillEllipsePixels.
func (c *Canvas) FillEllipse(brush Brush, bounds Rectangle) error {
return c.ellipse(brush, nullPenSingleton, bounds, 1)
}
// FillEllipsePixels draws a filled in native pixels.
func (c *Canvas) FillEllipsePixels(brush Brush, bounds Rectangle) error {
return c.ellipsePixels(brush, nullPenSingleton, bounds, 1)
}
// DrawImage draws image at given location (upper left) in 1/96" units unstretched.
//
// Deprecated: Newer applications should use DrawImagePixels.
func (c *Canvas) DrawImage(image Image, location Point) error {
return c.DrawImagePixels(image, PointFrom96DPI(location, c.DPI()))
}
// DrawImagePixels draws image at given location (upper left) in native pixels unstretched.
func (c *Canvas) DrawImagePixels(image Image, location Point) error {
if image == nil {
return newError("image cannot be nil")
}
return image.draw(c.hdc, location)
}
// DrawImageStretched draws image at given location in 1/96" units stretched.
//
// Deprecated: Newer applications should use DrawImageStretchedPixels.
func (c *Canvas) DrawImageStretched(image Image, bounds Rectangle) error {
return c.DrawImageStretchedPixels(image, RectangleFrom96DPI(bounds, c.DPI()))
}
// DrawImageStretchedPixels draws image at given location in native pixels stretched.
func (c *Canvas) DrawImageStretchedPixels(image Image, bounds Rectangle) error {
if image == nil {
return newError("image cannot be nil")
}
if dsoc, ok := image.(interface {
drawStretchedOnCanvasPixels(canvas *Canvas, bounds Rectangle) error
}); ok {
return dsoc.drawStretchedOnCanvasPixels(c, bounds)
}
return image.drawStretched(c.hdc, bounds)
}
// DrawBitmapWithOpacity draws bitmap with opacity at given location in 1/96" units stretched.
//
// Deprecated: Newer applications should use DrawBitmapWithOpacityPixels.
func (c *Canvas) DrawBitmapWithOpacity(bmp *Bitmap, bounds Rectangle, opacity byte) error {
return c.DrawBitmapWithOpacityPixels(bmp, RectangleFrom96DPI(bounds, c.DPI()), opacity)
}
// DrawBitmapWithOpacityPixels draws bitmap with opacity at given location in native pixels
// stretched.
func (c *Canvas) DrawBitmapWithOpacityPixels(bmp *Bitmap, bounds Rectangle, opacity byte) error {
if bmp == nil {
return newError("bmp cannot be nil")
}
return bmp.alphaBlend(c.hdc, bounds, opacity)
}
// DrawBitmapPart draws bitmap at given location in native pixels.
func (c *Canvas) DrawBitmapPart(bmp *Bitmap, dst, src Rectangle) error {
return c.DrawBitmapPartWithOpacityPixels(bmp, dst, src, 0xff)
}
// DrawBitmapPartWithOpacity draws bitmap at given location in 1/96" units.
//
// Deprecated: Newer applications should use DrawBitmapPartWithOpacityPixels.
func (c *Canvas) DrawBitmapPartWithOpacity(bmp *Bitmap, dst, src Rectangle, opacity byte) error {
dpi := c.DPI()
return c.DrawBitmapPartWithOpacityPixels(bmp, RectangleFrom96DPI(dst, dpi), RectangleFrom96DPI(src, dpi), opacity)
}
// DrawBitmapPartWithOpacityPixels draws bitmap at given location in native pixels.
func (c *Canvas) DrawBitmapPartWithOpacityPixels(bmp *Bitmap, dst, src Rectangle, opacity byte) error {
if bmp == nil {
return newError("bmp cannot be nil")
}
return bmp.alphaBlendPart(c.hdc, dst, src, opacity)
}
// DrawLine draws a line between two points in 1/96" units.
//
// Deprecated: Newer applications should use DrawLinePixels.
func (c *Canvas) DrawLine(pen Pen, from, to Point) error {
dpi := c.DPI()
return c.DrawLinePixels(pen, PointFrom96DPI(from, dpi), PointFrom96DPI(to, dpi))
}
// DrawLinePixels draws a line between two points in native pixels.
func (c *Canvas) DrawLinePixels(pen Pen, from, to Point) error {
if !win.MoveToEx(c.hdc, int(from.X), int(from.Y), nil) {
return newError("MoveToEx failed")
}
return c.withPen(pen, func() error {
if !win.LineTo(c.hdc, int32(to.X), int32(to.Y)) {
return newError("LineTo failed")
}
return nil
})
}
// DrawLine draws a line between given points in 1/96" units.
//
// Deprecated: Newer applications should use DrawLinePixels.
func (c *Canvas) DrawPolyline(pen Pen, points []Point) error {
if len(points) < 1 {
return nil
}
dpi := c.DPI()
pts := make([]win.POINT, len(points))
for i, p := range points {
pts[i] = PointFrom96DPI(p, dpi).toPOINT()
}
return c.withPen(pen, func() error {
if !win.Polyline(c.hdc, unsafe.Pointer(&pts[0].X), int32(len(pts))) {
return newError("Polyline failed")
}
return nil
})
}
// DrawPolylinePixels draws a line between given points in native pixels.
func (c *Canvas) DrawPolylinePixels(pen Pen, points []Point) error {
if len(points) < 1 {
return nil
}
pts := make([]win.POINT, len(points))
for i, p := range points {
pts[i] = p.toPOINT()
}
return c.withPen(pen, func() error {
if !win.Polyline(c.hdc, unsafe.Pointer(&pts[0].X), int32(len(pts))) {
return newError("Polyline failed")
}
return nil
})
}
// rectangle draws a rectangle in 1/96" units. sizeCorrection parameter is in native pixels.
//
// Deprecated: Newer applications should use rectanglePixels.
func (c *Canvas) rectangle(brush Brush, pen Pen, bounds Rectangle, sizeCorrection int) error {
return c.rectanglePixels(brush, pen, RectangleFrom96DPI(bounds, c.DPI()), sizeCorrection)
}
// rectanglePixels draws a rectangle in native pixels.
func (c *Canvas) rectanglePixels(brush Brush, pen Pen, bounds Rectangle, sizeCorrection int) error {
return c.withBrushAndPen(brush, pen, func() error {
if !win.Rectangle_(
c.hdc,
int32(bounds.X),
int32(bounds.Y),
int32(bounds.X+bounds.Width+sizeCorrection),
int32(bounds.Y+bounds.Height+sizeCorrection)) {
return newError("Rectangle_ failed")
}
return nil
})
}
// DrawRectangle draws a rectangle in 1/96" units.
//
// Deprecated: Newer applications should use DrawRectanglePixels.
func (c *Canvas) DrawRectangle(pen Pen, bounds Rectangle) error {
return c.rectangle(nullBrushSingleton, pen, bounds, 0)
}
// DrawRectanglePixels draws a rectangle in native pixels.
func (c *Canvas) DrawRectanglePixels(pen Pen, bounds Rectangle) error {
return c.rectanglePixels(nullBrushSingleton, pen, bounds, 0)
}
// FillRectangle draws a filled rectangle in 1/96" units.
//
// Deprecated: Newer applications should use FillRectanglePixels.
func (c *Canvas) FillRectangle(brush Brush, bounds Rectangle) error {
return c.rectangle(brush, nullPenSingleton, bounds, 1)
}
// FillRectanglePixels draws a filled rectangle in native pixels.
func (c *Canvas) FillRectanglePixels(brush Brush, bounds Rectangle) error {
return c.rectanglePixels(brush, nullPenSingleton, bounds, 1)
}
// roundedRectangle draws a rounded rectangle in 1/96" units. sizeCorrection parameter is in native
// pixels.
//
// Deprecated: Newer applications should use roundedRectanglePixels.
func (c *Canvas) roundedRectangle(brush Brush, pen Pen, bounds Rectangle, ellipseSize Size, sizeCorrection int) error {
dpi := c.DPI()
return c.roundedRectanglePixels(brush, pen, RectangleFrom96DPI(bounds, dpi), SizeFrom96DPI(ellipseSize, dpi), sizeCorrection)
}
// roundedRectanglePixels draws a rounded rectangle in native pixels.
func (c *Canvas) roundedRectanglePixels(brush Brush, pen Pen, bounds Rectangle, ellipseSize Size, sizeCorrection int) error {
return c.withBrushAndPen(brush, pen, func() error {
if !win.RoundRect(
c.hdc,
int32(bounds.X),
int32(bounds.Y),
int32(bounds.X+bounds.Width+sizeCorrection),
int32(bounds.Y+bounds.Height+sizeCorrection),
int32(ellipseSize.Width),
int32(ellipseSize.Height)) {
return newError("RoundRect failed")
}
return nil
})
}
// DrawRoundedRectangle draws a rounded rectangle in 1/96" units. sizeCorrection parameter is in native
// pixels.
//
// Deprecated: Newer applications should use DrawRoundedRectanglePixels.
func (c *Canvas) DrawRoundedRectangle(pen Pen, bounds Rectangle, ellipseSize Size) error {
return c.roundedRectangle(nullBrushSingleton, pen, bounds, ellipseSize, 0)
}
// DrawRoundedRectanglePixels draws a rounded rectangle in native pixels.
func (c *Canvas) DrawRoundedRectanglePixels(pen Pen, bounds Rectangle, ellipseSize Size) error {
return c.roundedRectanglePixels(nullBrushSingleton, pen, bounds, ellipseSize, 0)
}
// FillRoundedRectangle draws a filled rounded rectangle in 1/96" units. sizeCorrection parameter
// is in native
// pixels.
//
// Deprecated: Newer applications should use FillRoundedRectanglePixels.
func (c *Canvas) FillRoundedRectangle(brush Brush, bounds Rectangle, ellipseSize Size) error {
return c.roundedRectangle(brush, nullPenSingleton, bounds, ellipseSize, 1)
}
// FillRoundedRectanglePixels draws a filled rounded rectangle in native pixels.
func (c *Canvas) FillRoundedRectanglePixels(brush Brush, bounds Rectangle, ellipseSize Size) error {
return c.roundedRectanglePixels(brush, nullPenSingleton, bounds, ellipseSize, 1)
}
// GradientFillRectangle draws a gradient filled rectangle in 1/96" units.
//
// Deprecated: Newer applications should use GradientFillRectanglePixels.
func (c *Canvas) GradientFillRectangle(color1, color2 Color, orientation Orientation, bounds Rectangle) error {
return c.GradientFillRectanglePixels(color1, color2, orientation, RectangleFrom96DPI(bounds, c.DPI()))
}
// GradientFillRectanglePixels draws a gradient filled rectangle in native pixels.
func (c *Canvas) GradientFillRectanglePixels(color1, color2 Color, orientation Orientation, bounds Rectangle) error {
vertices := [2]win.TRIVERTEX{
{
X: int32(bounds.X),
Y: int32(bounds.Y),
Red: uint16(color1.R()) * 256,
Green: uint16(color1.G()) * 256,
Blue: uint16(color1.B()) * 256,
Alpha: 0,
}, {
X: int32(bounds.X + bounds.Width),
Y: int32(bounds.Y + bounds.Height),
Red: uint16(color2.R()) * 256,
Green: uint16(color2.G()) * 256,
Blue: uint16(color2.B()) * 256,
Alpha: 0,
},
}
indices := win.GRADIENT_RECT{
UpperLeft: 0,
LowerRight: 1,
}
var o uint32
if orientation == Vertical {
o = 1
}
if !win.GradientFill(c.hdc, &vertices[0], 2, unsafe.Pointer(&indices), 1, o) {
return newError("GradientFill failed")
}
return nil
}
// DrawText draws text at given location in 1/96" units.
//
// Deprecated: Newer applications should use DrawTextPixels.
func (c *Canvas) DrawText(text string, font *Font, color Color, bounds Rectangle, format DrawTextFormat) error {
return c.DrawTextPixels(text, font, color, RectangleFrom96DPI(bounds, c.DPI()), format)
}
// DrawTextPixels draws text at given location in native pixels.
func (c *Canvas) DrawTextPixels(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
})
}
// fontHeight returns font height in native pixels.
func (c *Canvas) fontHeight(font *Font) (height int, err error) {
err = c.withFontAndTextColor(font, 0, func() error {
var size win.SIZE
if !win.GetTextExtentPoint32(c.hdc, gM, 2, &size) {
return newError("GetTextExtentPoint32 failed")
}
height = int(size.CY)
if height == 0 {
return newError("invalid font height")
}
return nil
})
return
}
// measureTextForDPI measures text for given DPI. Input and output bounds are in native pixels.
func (c *Canvas) measureTextForDPI(text string, font *Font, bounds Rectangle, format DrawTextFormat, dpi int) (boundsMeasured Rectangle, err error) {
hFont := win.HGDIOBJ(font.handleForDPI(dpi))
oldHandle := win.SelectObject(c.hdc, hFont)
if oldHandle == 0 {
err = newError("SelectObject failed")
return
}
defer win.SelectObject(c.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_CALCRECT | win.DT_EDITCONTROL | win.DT_NOPREFIX | win.DT_WORDBREAK
height := win.DrawTextEx(
c.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),
}
return
}
// MeasureText measures text size. Input and output bounds are in 1/96" units.
//
// Deprecated: Newer applications should use MeasureTextPixels.
func (c *Canvas) MeasureText(text string, font *Font, bounds Rectangle, format DrawTextFormat) (boundsMeasured Rectangle, runesFitted int, err error) {
dpi := c.DPI()
var boundsMeasuredPixels Rectangle
boundsMeasuredPixels, runesFitted, err = c.MeasureTextPixels(text, font, RectangleFrom96DPI(bounds, dpi), format)
if err != nil {
return
}
boundsMeasured = RectangleTo96DPI(boundsMeasuredPixels, dpi)
return
}
// MeasureTextPixels measures text size. Input and output bounds are in native pixels.
func (c *Canvas) MeasureTextPixels(text string, font *Font, bounds Rectangle, format DrawTextFormat) (boundsMeasured Rectangle, runesFitted int, err error) {
boundsMeasured, _, runesFitted, err = c.measureAndModifyTextPixels(text, font, bounds, format)
return
}
// MeasureAndModifyTextPixels measures text size and also supports modification
// of the text which occurs if it does not fit into the specified bounds.
//
// Input and output bounds are in native pixels.
func (c *Canvas) MeasureAndModifyTextPixels(text string, font *Font, bounds Rectangle, format DrawTextFormat) (boundsMeasured Rectangle, textDisplayed string, err error) {
var textPtr *uint16
var runesFitted int
if boundsMeasured, textPtr, runesFitted, err = c.measureAndModifyTextPixels(text, font, bounds, format|TextModifyString); err != nil {
return
}
if runesFitted == utf8.RuneCountInString(text) {
textDisplayed = text
} else {
if format&(TextEndEllipsis|TextPathEllipsis) != 0 {
textDisplayed = win.UTF16PtrToString(textPtr)
} else {
textDisplayed = string(([]rune)(text)[:runesFitted])
}
}
return
}
func (c *Canvas) measureAndModifyTextPixels(text string, font *Font, bounds Rectangle, format DrawTextFormat) (boundsMeasured Rectangle, textPtr *uint16, 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, params.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.DPI()))
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),
}
textPtr = strPtr
runesFitted = int(params.UiLengthDrawn)
return
}