RichEdit: append random colored text demo

Author: whtiehack

examples/basic/main.go

@@ -3,6 +3,7 @@ package main
 import (
 	"fmt"
 	"log"
+	"math/rand"
 	"os"
 	"strconv"
 	"sync/atomic"
@@ -14,6 +15,7 @@ import (
 
 func init() {
 	log.SetOutput(os.Stdout)
+	rand.Seed(time.Now().UnixNano())
 }
 
 var dlg *wingui.Dialog
@@ -349,7 +351,11 @@ func bindWidgets(dlg *wingui.Dialog) {
 
 	appendBtn, _ := wingui.BindNewButton(IDC_RICH_APPEND, richPage)
 	appendBtn.OnClicked = func() {
-		rich.AppendText(time.Now().Format("15:04:05") + " hello rich edit\r\n")
+		r := uint32(60 + rand.Intn(160))
+		g := uint32(60 + rand.Intn(160))
+		b := uint32(60 + rand.Intn(160))
+		color := win.COLORREF(r | (g << 8) | (b << 16))
+		rich.AppendTextColor(time.Now().Format("15:04:05")+" hello rich edit\r\n", color)
 		updateRichLabel()
 	}
 	clearBtn, _ := wingui.BindNewButton(IDC_RICH_CLEAR, richPage)

richedit.go

@@ -7,6 +7,37 @@ import (
 	"github.com/lxn/win"
 )
 
+const (
+	emSetCharFormat = win.WM_USER + 68
+
+	scfSelection = 0x0001
+
+	cfmColor = 0x40000000
+)
+
+type charformat2W struct {
+	cbSize        uint32
+	dwMask        uint32
+	dwEffects     uint32
+	yHeight       int32
+	yOffset       int32
+	crTextColor   win.COLORREF
+	bCharSet      byte
+	bPitchAndFam  byte
+	szFaceName    [32]uint16
+	wWeight       uint16
+	sSpacing      int16
+	crBackColor   win.COLORREF
+	lcid          uint32
+	dwReserved    uint32
+	sStyle        int16
+	wKerning      uint16
+	bUnderlineTyp byte
+	bAnimation    byte
+	bRevAuthor    byte
+	bReserved1    byte
+}
+
 // RichEdit is a wrapper for the Win32 Rich Edit control.
 // The class is provided by Msftedit.dll (RICHEDIT50W) or Riched20.dll (RichEdit20W).
 type RichEdit struct {
@@ -75,6 +106,26 @@ func (re *RichEdit) AppendText(value string) {
 	re.SetTextSelection(s, e)
 }
 
+// SetSelectionTextColor sets the selected text (and typing attributes) color.
+func (re *RichEdit) SetSelectionTextColor(color win.COLORREF) bool {
+	cf := charformat2W{
+		cbSize:      uint32(unsafe.Sizeof(charformat2W{})),
+		dwMask:      cfmColor,
+		crTextColor: color,
+	}
+	ret := re.SendMessage(emSetCharFormat, scfSelection, uintptr(unsafe.Pointer(&cf)))
+	return ret != 0
+}
+
+// AppendTextColor appends text with a specific color.
+func (re *RichEdit) AppendTextColor(value string, color win.COLORREF) {
+	l := re.TextLength()
+	re.SetTextSelection(l, l)
+	_ = re.SetSelectionTextColor(color)
+	re.ReplaceSelectedText(value, false)
+	_ = re.SetSelectionTextColor(win.COLORREF(0))
+}
+
 // TextLength returns current text length.
 func (re *RichEdit) TextLength() int {
 	return int(re.SendMessage(win.WM_GETTEXTLENGTH, 0, 0))