feat: Refactor of Go backend code

app_screenshot.go

@@ -0,0 +1,164 @@
+// Package main provides screenshot functionality for EMLy.
+// This file contains methods for capturing, saving, and exporting screenshots
+// of the application window.
+package main
+
+import (
+	"encoding/base64"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"emly/backend/utils"
+
+	"github.com/wailsapp/wails/v2/pkg/runtime"
+)
+
+// =============================================================================
+// Screenshot Types
+// =============================================================================
+
+// ScreenshotResult contains the captured screenshot data and metadata.
+type ScreenshotResult struct {
+	// Data is the base64-encoded PNG image data
+	Data string `json:"data"`
+	// Width is the image width in pixels
+	Width int `json:"width"`
+	// Height is the image height in pixels
+	Height int `json:"height"`
+	// Filename is the suggested filename for saving
+	Filename string `json:"filename"`
+}
+
+// =============================================================================
+// Screenshot Methods
+// =============================================================================
+
+// TakeScreenshot captures the current EMLy application window and returns it as base64 PNG.
+// This uses Windows GDI API to capture the window contents, handling DWM composition
+// for proper rendering of modern Windows applications.
+//
+// The method automatically detects whether the app is in main mode or viewer mode
+// and captures the appropriate window.
+//
+// Returns:
+//   - *ScreenshotResult: Contains base64 PNG data, dimensions, and suggested filename
+//   - error: Error if window capture or encoding fails
+func (a *App) TakeScreenshot() (*ScreenshotResult, error) {
+	// Determine window title based on current mode
+	windowTitle := "EMLy - EML Viewer for 3gIT"
+
+	// Check if running in viewer mode
+	for _, arg := range os.Args {
+		if strings.Contains(arg, "--view-image") {
+			windowTitle = "EMLy Image Viewer"
+			break
+		}
+		if strings.Contains(arg, "--view-pdf") {
+			windowTitle = "EMLy PDF Viewer"
+			break
+		}
+	}
+
+	// Capture the window using Windows GDI API
+	img, err := utils.CaptureWindowByTitle(windowTitle)
+	if err != nil {
+		return nil, fmt.Errorf("failed to capture window: %w", err)
+	}
+
+	// Encode to PNG and convert to base64
+	base64Data, err := utils.ScreenshotToBase64PNG(img)
+	if err != nil {
+		return nil, fmt.Errorf("failed to encode screenshot: %w", err)
+	}
+
+	// Build result with metadata
+	bounds := img.Bounds()
+	timestamp := time.Now().Format("20060102_150405")
+
+	return &ScreenshotResult{
+		Data:     base64Data,
+		Width:    bounds.Dx(),
+		Height:   bounds.Dy(),
+		Filename: fmt.Sprintf("emly_screenshot_%s.png", timestamp),
+	}, nil
+}
+
+// SaveScreenshot captures and saves the screenshot to the system temp directory.
+// This is a convenience method that captures and saves in one step.
+//
+// Returns:
+//   - string: The full path to the saved screenshot file
+//   - error: Error if capture or save fails
+func (a *App) SaveScreenshot() (string, error) {
+	// Capture the screenshot
+	result, err := a.TakeScreenshot()
+	if err != nil {
+		return "", err
+	}
+
+	// Decode base64 data
+	data, err := base64.StdEncoding.DecodeString(result.Data)
+	if err != nil {
+		return "", fmt.Errorf("failed to decode screenshot data: %w", err)
+	}
+
+	// Save to temp directory
+	tempDir := os.TempDir()
+	filePath := filepath.Join(tempDir, result.Filename)
+
+	if err := os.WriteFile(filePath, data, 0644); err != nil {
+		return "", fmt.Errorf("failed to save screenshot: %w", err)
+	}
+
+	return filePath, nil
+}
+
+// SaveScreenshotAs captures a screenshot and opens a save dialog for the user
+// to choose where to save it.
+//
+// Returns:
+//   - string: The selected save path, or empty string if cancelled
+//   - error: Error if capture, dialog, or save fails
+func (a *App) SaveScreenshotAs() (string, error) {
+	// Capture the screenshot first
+	result, err := a.TakeScreenshot()
+	if err != nil {
+		return "", err
+	}
+
+	// Open save dialog with PNG filter
+	savePath, err := runtime.SaveFileDialog(a.ctx, runtime.SaveDialogOptions{
+		DefaultFilename: result.Filename,
+		Title:           "Save Screenshot",
+		Filters: []runtime.FileFilter{
+			{
+				DisplayName: "PNG Images (*.png)",
+				Pattern:     "*.png",
+			},
+		},
+	})
+	if err != nil {
+		return "", fmt.Errorf("failed to open save dialog: %w", err)
+	}
+
+	// User cancelled
+	if savePath == "" {
+		return "", nil
+	}
+
+	// Decode base64 data
+	data, err := base64.StdEncoding.DecodeString(result.Data)
+	if err != nil {
+		return "", fmt.Errorf("failed to decode screenshot data: %w", err)
+	}
+
+	// Save to selected location
+	if err := os.WriteFile(savePath, data, 0644); err != nil {
+		return "", fmt.Errorf("failed to save screenshot: %w", err)
+	}
+
+	return savePath, nil
+}