Merge pull request #1696 from andydotxyz/fix/svgdetection

Improve detection of SVG from resources in case name was wrong

internal/painter/image.go

@@ -28,19 +28,24 @@ func PaintImage(img *canvas.Image, c fyne.Canvas, width, height int) image.Image
 
 	switch {
 	case img.File != "" || img.Resource != nil:
-		var file io.Reader
-		var name string
+		var (
+			file  io.Reader
+			name  string
+			isSVG bool
+		)
 		if img.Resource != nil {
 			name = img.Resource.Name()
 			file = bytes.NewReader(img.Resource.Content())
+			isSVG = isResourceSVG(img.Resource)
 		} else {
 			name = img.File
 			handle, _ := os.Open(img.File)
 			defer handle.Close()
 			file = handle
+			isSVG = isFileSVG(img.File)
 		}
 
-		if strings.ToLower(filepath.Ext(name)) == ".svg" {
+		if isSVG {
 			tex := svgCacheGet(name, width, height)
 			if tex == nil {
 				// Not in cache, so load the item and add to cache
@@ -163,3 +168,23 @@ func checkImageMinSize(img *canvas.Image, c fyne.Canvas, pixX, pixY int) bool {
 
 	return true
 }
+
+func isFileSVG(path string) bool {
+	return strings.ToLower(filepath.Ext(path)) == ".svg"
+}
+
+func isResourceSVG(res fyne.Resource) bool {
+	if strings.ToLower(filepath.Ext(res.Name())) == ".svg" {
+		return true
+	}
+
+	if len(res.Content()) < 5 {
+		return false
+	}
+
+	switch strings.ToLower(string(res.Content()[:5])) {
+	case "<!doc", "<?xml", "<svg ":
+		return true
+	}
+	return false
+}

internal/painter/image_internal_test.go

@@ -0,0 +1,32 @@
+package painter
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"fyne.io/fyne"
+)
+
+func TestIsFileSVG(t *testing.T) {
+	assert.True(t, isFileSVG("test.svg"))
+	assert.True(t, isFileSVG("test.SVG"))
+	assert.False(t, isFileSVG("testsvg"))
+	assert.False(t, isFileSVG("test.png"))
+}
+
+func TestIsResourceSVG(t *testing.T) {
+	res, err := fyne.LoadResourceFromPath("./testdata/stroke.svg")
+	assert.Nil(t, err)
+	assert.True(t, isResourceSVG(res))
+
+	res.(*fyne.StaticResource).StaticName = "stroke"
+	assert.True(t, isResourceSVG(res))
+
+	svgString := "<svg version=\"1.1\"></svg>"
+	res.(*fyne.StaticResource).StaticContent = []byte(svgString)
+	assert.True(t, isResourceSVG(res))
+
+	res.(*fyne.StaticResource).StaticContent = []byte("<?xml version=\"1.0\" encoding=\"utf-8\"?>\n" + svgString)
+	assert.True(t, isResourceSVG(res))
+}