Set Window Background colour if provided + debounce redraw option

v2/go.mod

@@ -42,6 +42,7 @@ require github.com/bitfield/script v0.19.0
 require (
 	bitbucket.org/creachadair/shell v0.0.7 // indirect
 	github.com/Microsoft/go-winio v0.4.16 // indirect
+	github.com/bep/debounce v1.2.1 // indirect
 	github.com/emirpasic/gods v1.12.0 // indirect
 	github.com/go-git/gcfg v1.5.0 // indirect
 	github.com/go-ole/go-ole v1.2.6 // indirect

v2/go.sum

@@ -11,6 +11,8 @@ github.com/anmitsu/go-shlex v0.0.0-20161002113705-648efa622239 h1:kFOfPq6dUM1hTo
 github.com/anmitsu/go-shlex v0.0.0-20161002113705-648efa622239/go.mod h1:2FmKhYUyUczH0OGQWaF5ceTx0UBShxjsH6f8oGKYe2c=
 github.com/armon/go-socks5 v0.0.0-20160902184237-e75332964ef5 h1:0CwZNZbxp69SHPdPJAN/hZIm0C4OItdklCFmMRWYpio=
 github.com/armon/go-socks5 v0.0.0-20160902184237-e75332964ef5/go.mod h1:wHh0iHkYZB8zMSxRWpUBQtwG5a7fFgvEO+odwuTv2gs=
+github.com/bep/debounce v1.2.1 h1:v67fRdBA9UQu2NhLFXrSg0Brw7CexQekrBwDMM8bzeY=
+github.com/bep/debounce v1.2.1/go.mod h1:H8yggRPQKLUhUoqrJC1bO2xNya7vanpDl7xR3ISbCJ0=
 github.com/bitfield/script v0.19.0 h1:W24f+FQuPab9gXcW8bhcbo5qO8AtrXyu3XOnR4zhHN0=
 github.com/bitfield/script v0.19.0/go.mod h1:ana6F8YOSZ3ImT8SauIzuYSqXgFVkSUJ6kgja+WMmIY=
 github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=

v2/internal/frontend/desktop/windows/frontend.go

@@ -7,27 +7,28 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"github.com/wailsapp/wails/v2/internal/frontend/desktop/windows/win32"
-	"io"
-	"log"
-	"net/http"
-	"net/http/httptest"
-	"net/url"
-	"runtime"
-	"strconv"
-	"strings"
-	"text/template"
-
+	"github.com/bep/debounce"
 	"github.com/wailsapp/wails/v2/internal/binding"
 	"github.com/wailsapp/wails/v2/internal/frontend"
 	"github.com/wailsapp/wails/v2/internal/frontend/assetserver"
 	"github.com/wailsapp/wails/v2/internal/frontend/desktop/windows/go-webview2/pkg/edge"
+	"github.com/wailsapp/wails/v2/internal/frontend/desktop/windows/win32"
 	"github.com/wailsapp/wails/v2/internal/frontend/desktop/windows/winc"
 	"github.com/wailsapp/wails/v2/internal/frontend/desktop/windows/winc/w32"
 	"github.com/wailsapp/wails/v2/internal/logger"
 	"github.com/wailsapp/wails/v2/internal/system/operatingsystem"
 	"github.com/wailsapp/wails/v2/pkg/options"
 	"github.com/wailsapp/wails/v2/pkg/options/windows"
+	"io"
+	"log"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"runtime"
+	"strconv"
+	"strings"
+	"text/template"
+	"time"
 )
 
 const startURL = "http://wails.localhost/"
@@ -54,7 +55,8 @@ type Frontend struct {
 	hasStarted bool
 
 	// Windows build number
-	versionInfo *operatingsystem.WindowsVersionInfo
+	versionInfo     *operatingsystem.WindowsVersionInfo
+	resizeDebouncer func(f func())
 }
 
 func NewFrontend(ctx context.Context, appoptions *options.App, myLogger *logger.Logger, appBindings *binding.Bindings, dispatcher frontend.Dispatcher) *Frontend {
@@ -71,6 +73,12 @@ func NewFrontend(ctx context.Context, appoptions *options.App, myLogger *logger.
 		versionInfo:     versionInfo,
 	}
 
+	if appoptions.Windows != nil {
+		if appoptions.Windows.ResizeDebounceMS > 0 {
+			result.resizeDebouncer = debounce.New(time.Duration(appoptions.Windows.ResizeDebounceMS) * time.Millisecond)
+		}
+	}
+
 	// We currently can't use wails://wails/ as other platforms do, therefore we map the assets sever onto the following url.
 	result.startURL, _ = url.Parse(startURL)
 
@@ -151,7 +159,15 @@ func (f *Frontend) Run(ctx context.Context) error {
 			}
 		}
 
-		f.chromium.Resize()
+		if f.resizeDebouncer != nil {
+			f.resizeDebouncer(func() {
+				f.mainWindow.Invoke(func() {
+					f.chromium.Resize()
+				})
+			})
+		} else {
+			f.chromium.Resize()
+		}
 	})
 
 	mainWindow.OnClose().Bind(func(arg *winc.Event) {
@@ -329,6 +345,7 @@ func (f *Frontend) WindowSetRGBA(col *options.RGBA) {
 			log.Fatal(err)
 		}
 	})
+
 }
 
 func (f *Frontend) Quit() {

v2/internal/frontend/desktop/windows/win32/consts.go

@@ -15,13 +15,19 @@ var (
 	moduser32                = syscall.NewLazyDLL("user32.dll")
 	procSystemParametersInfo = moduser32.NewProc("SystemParametersInfoW")
 	procGetWindowLong        = moduser32.NewProc("GetWindowLongW")
+	procSetClassLongPtr      = moduser32.NewProc("SetClassLongPtrW")
 	procShowWindow           = moduser32.NewProc("ShowWindow")
 )
 var (
 	moddwmapi                        = syscall.NewLazyDLL("dwmapi.dll")
 	procDwmSetWindowAttribute        = moddwmapi.NewProc("DwmSetWindowAttribute")
 	procDwmExtendFrameIntoClientArea = moddwmapi.NewProc("DwmExtendFrameIntoClientArea")
 )
+var (
+	modwingdi            = syscall.NewLazyDLL("gdi32.dll")
+	procCreateSolidBrush = modwingdi.NewProc("CreateSolidBrush")
+)
+
 var windowsVersion, _ = operatingsystem.GetWindowsVersionInfo()
 
 func IsWindowsVersionAtLeast(major, minor, buildNumber int) bool {

v2/internal/frontend/desktop/windows/win32/window.go

@@ -4,6 +4,7 @@ package win32
 
 import (
 	"fmt"
+	"github.com/wailsapp/wails/v2/internal/frontend/desktop/windows/winc"
 	"log"
 	"syscall"
 	"unsafe"
@@ -33,6 +34,10 @@ const (
 	SW_FORCEMINIMIZE   = 11
 )
 
+const (
+	GCLP_HBRBACKGROUND int32 = -10
+)
+
 // http://msdn.microsoft.com/en-us/library/windows/desktop/bb773244.aspx
 type MARGINS struct {
 	CxLeftWidth, CxRightWidth, CyTopHeight, CyBottomHeight int32
@@ -74,6 +79,12 @@ func ShowWindowMinimised(hwnd uintptr) {
 	showWindow(hwnd, SW_MINIMIZE)
 }
 
+func SetBackgroundColour(hwnd uintptr, r, g, b uint8) {
+	col := winc.RGB(r, g, b)
+	hbrush, _, _ := procCreateSolidBrush.Call(uintptr(col))
+	setClassLongPtr(hwnd, GCLP_HBRBACKGROUND, hbrush)
+}
+
 func dwmExtendFrameIntoClientArea(hwnd uintptr, margins *MARGINS) error {
 	ret, _, _ := procDwmExtendFrameIntoClientArea.Call(
 		hwnd,
@@ -86,6 +97,15 @@ func dwmExtendFrameIntoClientArea(hwnd uintptr, margins *MARGINS) error {
 	return nil
 }
 
+func setClassLongPtr(hwnd uintptr, param int32, val uintptr) bool {
+	ret, _, _ := procSetClassLongPtr.Call(
+		hwnd,
+		uintptr(param),
+		val,
+	)
+	return ret != 0
+}
+
 func getWindowLong(hwnd uintptr, index int) int32 {
 	ret, _, _ := procGetWindowLong.Call(
 		hwnd,

v2/internal/frontend/desktop/windows/window.go

@@ -3,9 +3,10 @@
 package windows
 
 import (
+	"unsafe"
+
 	"github.com/wailsapp/wails/v2/internal/frontend/desktop/windows/win32"
 	"github.com/wailsapp/wails/v2/internal/system/operatingsystem"
-	"unsafe"
 
 	"github.com/wailsapp/wails/v2/internal/frontend/desktop/windows/winc"
 	"github.com/wailsapp/wails/v2/internal/frontend/desktop/windows/winc/w32"
@@ -66,6 +67,10 @@ func NewWindow(parent winc.Controller, appoptions *options.App, versionInfo *ope
 		}
 	}
 
+	if appoptions.RGBA != nil {
+		win32.SetBackgroundColour(result.Handle(), appoptions.RGBA.R, appoptions.RGBA.G, appoptions.RGBA.B)
+	}
+
 	result.SetSize(appoptions.Width, appoptions.Height)
 	result.SetText(appoptions.Title)
 	result.EnableSizable(!appoptions.DisableResize)
@@ -191,6 +196,8 @@ func (w *Window) WndProc(msg uint32, wparam, lparam uintptr) uintptr {
 			// This hides the titlebar and also disables the resizing from user interaction because the standard frame is not
 			// shown. We still need the WS_THICKFRAME style to enable resizing from the frontend.
 			if wparam != 0 {
+				rgrc := (*w32.RECT)(unsafe.Pointer(lparam))
+
 				style := uint32(w32.GetWindowLong(w.Handle(), w32.GWL_STYLE))
 				if style&w32.WS_MAXIMIZE != 0 {
 					// If the window is maximized we must adjust the client area to the work area of the monitor. Otherwise
@@ -200,7 +207,6 @@ func (w *Window) WndProc(msg uint32, wparam, lparam uintptr) uintptr {
 					var monitorInfo w32.MONITORINFO
 					monitorInfo.CbSize = uint32(unsafe.Sizeof(monitorInfo))
 					if w32.GetMonitorInfo(monitor, &monitorInfo) {
-						rgrc := (*w32.RECT)(unsafe.Pointer(lparam))
 						*rgrc = monitorInfo.RcWork
 
 						maxWidth := w.frontendOptions.MaxWidth
@@ -220,6 +226,10 @@ func (w *Window) WndProc(msg uint32, wparam, lparam uintptr) uintptr {
 							}
 						}
 					}
+				} else {
+					// This is needed to workaround the resize flickering in frameless mode with WindowDecorations
+					// See: https://stackoverflow.com/a/6558508
+					rgrc.Bottom -= 1
 				}
 
 				return 0

v2/pkg/options/windows/windows.go

@@ -82,6 +82,10 @@ type Options struct {
 
 	// User messages that can be customised
 	Messages *Messages
+
+	// ResizeDebounceMS is the amount of time to debounce redraws of webview2
+	// when resizing the window
+	ResizeDebounceMS uint16
 }
 
 func DefaultMessages() *Messages {

website/docs/reference/options.mdx

@@ -511,6 +511,15 @@ Type: `*windows.Messages`
 A struct of strings used by the webview2 installer if a valid webview2 runtime is not found.
 Customise this for any language you choose to support.
 
+### ResizeDebounceMS
+
+Name: ResizeDebounceMS
+
+Type: uint16
+
+ResizeDebounceMS is the amount of time to debounce redraws of webview2 when resizing the window.
+The default value (0) will perform redraws as fast as it can.
+
 ## Mac Specific Options
 
 ### TitleBar