[V3 alpha] Fix ultrawide monitor support on Wayland (fixes #4429) (#4561)

* Fixed Wayland related window maximum size issues on ultrawide monitors by adding a monitor-window search fallback.

* Fixed Wayland related window maximum size issues on ultrawide monitors by adding a monitor-window search fallback.

* Added note to UNRELEASED_CHANGELOG.md regarding Wayland ultrawide monitor fix of issue 4439.

---------

Co-authored-by: Lea Anthony <lea.anthony@gmail.com>

v3/UNRELEASED_CHANGELOG.md

@@ -23,6 +23,7 @@ After processing, the content will be moved to the main changelog and this file
 
 ## Fixed
 <!-- Bug fixes -->
+- Fixed Wayland window size maximising issues (https://github.com/wailsapp/wails/issues/4429) by [@samstanier](https://github.com/samstanier)
 
 ## Deprecated
 <!-- Soon-to-be removed features -->

v3/cmd/wails3/main.go

@@ -33,16 +33,16 @@ func main() {
 	app := clir.NewCli("wails", "The Wails3 CLI", "v3")
 	app.NewSubCommand("docs", "Open the docs").Action(openDocs)
 	app.NewSubCommandFunction("init", "Initialise a new project", commands.Init)
-	
+
 	build := app.NewSubCommand("build", "Build the project")
 	var buildFlags flags.Build
 	build.AddFlags(&buildFlags)
 	build.Action(func() error {
 		return commands.Build(&buildFlags, build.OtherArgs())
 	})
-	
+
 	app.NewSubCommandFunction("dev", "Run in Dev mode", commands.Dev)
-	
+
 	pkg := app.NewSubCommand("package", "Package application")
 	var pkgFlags flags.Package
 	pkg.AddFlags(&pkgFlags)

v3/pkg/application/linux_cgo.go

@@ -284,17 +284,17 @@ func getLinuxWebviewWindow(window Window) *linuxWebviewWindow {
 	if window == nil {
 		return nil
 	}
-	
+
 	webviewWindow, ok := window.(*WebviewWindow)
 	if !ok {
 		return nil
 	}
-	
+
 	lw, ok := webviewWindow.impl.(*linuxWebviewWindow)
 	if !ok {
 		return nil
 	}
-	
+
 	return lw
 }
 
@@ -928,13 +928,33 @@ func (w *linuxWebviewWindow) fullscreen() {
 }
 
 func (w *linuxWebviewWindow) getCurrentMonitor() *C.GdkMonitor {
-	// Get the monitor that the window is currently on
 	display := C.gtk_widget_get_display(w.gtkWidget())
 	gdkWindow := C.gtk_widget_get_window(w.gtkWidget())
-	if gdkWindow == nil {
-		return nil
+	if gdkWindow != nil {
+		monitor := C.gdk_display_get_monitor_at_window(display, gdkWindow)
+		if monitor != nil {
+			return monitor
+		}
 	}
-	return C.gdk_display_get_monitor_at_window(display, gdkWindow)
+
+	// Wayland fallback: find monitor containing the current window
+	n_monitors := C.gdk_display_get_n_monitors(display)
+	window_x, window_y := w.position()
+	for i := 0; i < int(n_monitors); i++ {
+		test_monitor := C.gdk_display_get_monitor(display, C.int(i))
+		if test_monitor != nil {
+			var rect C.GdkRectangle
+			C.gdk_monitor_get_geometry(test_monitor, &rect)
+
+			// Check if window is within this monitor's bounds
+			if window_x >= int(rect.x) && window_x < int(rect.x+rect.width) &&
+				window_y >= int(rect.y) && window_y < int(rect.y+rect.height) {
+				return test_monitor
+			}
+		}
+	}
+
+	return nil
 }
 
 func (w *linuxWebviewWindow) getScreen() (*Screen, error) {

v3/pkg/application/webview_window_linux.go

@@ -6,12 +6,13 @@ import (
 	"fmt"
 	"time"
 
+	"unsafe"
+
 	"github.com/bep/debounce"
 	"github.com/wailsapp/wails/v3/internal/assetserver"
 	"github.com/wailsapp/wails/v3/internal/capabilities"
 	"github.com/wailsapp/wails/v3/internal/runtime"
 	"github.com/wailsapp/wails/v3/pkg/events"
-	"unsafe"
 )
 
 type dragInfo struct {