Adjustments on GUI handling

gui/window.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"image"
 	"image/color"
+	"os"
 
 	"gioui.org/app"
 	"gioui.org/io/key"
@@ -35,6 +36,9 @@ func (ui *GUI) Draw() error {
 	), app.Title(ui.title))
 
 	if err := ui.Run(w); err != nil {
+		defer func() {
+			os.Exit(0)
+		}()
 		return fmt.Errorf("GUI rendering error: %w", err)
 	}
 

main.go

@@ -12,6 +12,7 @@ import (
 	"os"
 	"time"
 
+	"gioui.org/app"
 	"github.com/esimov/diagram/canvas"
 	"github.com/esimov/diagram/gui"
 	"github.com/esimov/diagram/io"
@@ -79,4 +80,6 @@ func main() {
 	} else {
 		ui.InitApp(*fontPath)
 	}
+
+	go app.Main()
 }

ui/panels.go

@@ -3,6 +3,7 @@ package ui
 import (
 	"fmt"
 	"image"
+	"log"
 	"math"
 	"os"
 	"path/filepath"
@@ -474,34 +475,35 @@ func (ui *UI) generateDiagram(name string) error {
 		})
 	})
 
-	defer func() error {
+	defer func() {
 		if err == nil {
 			diagram := filePath + output
 			f, err := os.Open(diagram)
 			if err != nil {
-				return fmt.Errorf("failed opening the image %q: %w", diagram, err)
+				log.Fatalf("failed opening the image %q: %v", diagram, err)
 			}
 
 			source, _, err := image.Decode(f)
 			if err != nil {
-				return fmt.Errorf("failed to decode the image %q: %w", diagram, err)
+				log.Fatalf("failed to decode the image %q: %v", diagram, err)
 			}
 
-			gui := gui.NewGUI(source, "Diagram preview")
-			go func() error {
-				if err := gui.Draw(); err != nil {
-					return fmt.Errorf("error drawing the diagram: %w", err)
-				}
-				return nil
-			}()
+			// Lunch Gio GUI thread.
+			go ui.showPreview(source, "Diagram preview")
 		}
-
-		return nil
 	}()
 
 	return nil
 }
 
+func (ui *UI) showPreview(img image.Image, title string) {
+	gui := gui.NewGUI(img, title)
+
+	if err := gui.Draw(); err != nil {
+		log.Fatalf("error drawing the diagram: %v", err)
+	}
+}
+
 // showSaveModal show the save modal.
 func (ui *UI) showSaveModal(name string) error {
 	var saveBtn, cancelBtn *gocui.View