From 4a5cc2dd260ee1675f40d581ed06141459f60179 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Julius=20K=C3=BCnzel?= <julius.kuenzel@kde.org>
Date: Mon, 6 Jan 2025 20:31:18 +0100
Subject: [PATCH] images.Text: Add "alignx" option for horizontal alignment

Add an "alignx" option to the images.Text to control whether the value of the "x" option is the left border of the text (current behaviour), the center of each line or the right border.

Fixes #10849
---
 docs/content/en/functions/images/Text.md |  4 ++
 resources/images/filters.go              |  7 +++
 resources/images/text.go                 | 59 ++++++++++++++++++------
 3 files changed, 57 insertions(+), 13 deletions(-)

diff --git a/docs/content/en/functions/images/Text.md b/docs/content/en/functions/images/Text.md
index 8c6670d42..6a18468b7 100644
--- a/docs/content/en/functions/images/Text.md
+++ b/docs/content/en/functions/images/Text.md
@@ -37,6 +37,10 @@ x
 y
 : (`int`) The vertical offset, in pixels, relative to the top of the image. Default is `10`.
 
+alignx
+ {{< new-in 0.141.0 >}}
+: (`string`) The horizontal alignment of the text relative to the `x` position. One of `left`, `center`, or `right`. Default is `left`.
+
 [global resource]: /getting-started/glossary/#global-resource
 [page resource]: /getting-started/glossary/#page-resource
 [remote resource]: /getting-started/glossary/#remote-resource
diff --git a/resources/images/filters.go b/resources/images/filters.go
index 0a620716d..99fecdf20 100644
--- a/resources/images/filters.go
+++ b/resources/images/filters.go
@@ -69,6 +69,7 @@ func (*Filters) Text(text string, options ...any) gift.Filter {
 		size:        20,
 		x:           10,
 		y:           10,
+		alignx:      "left",
 		linespacing: 2,
 	}
 
@@ -87,6 +88,12 @@ func (*Filters) Text(text string, options ...any) gift.Filter {
 				tf.x = cast.ToInt(v)
 			case "y":
 				tf.y = cast.ToInt(v)
+			case "alignx":
+				tf.alignx = cast.ToString(v)
+				if tf.alignx != "left" && tf.alignx != "center" && tf.alignx != "right" {
+					panic("alignx must be one of left, center, right")
+				}
+
 			case "linespacing":
 				tf.linespacing = cast.ToInt(v)
 			case "font":
diff --git a/resources/images/text.go b/resources/images/text.go
index c1abc60bd..324878839 100644
--- a/resources/images/text.go
+++ b/resources/images/text.go
@@ -35,6 +35,7 @@ type textFilter struct {
 	text        string
 	color       color.Color
 	x, y        int
+	alignx      string
 	size        float64
 	linespacing int
 	fontSource  hugio.ReadSeekCloserProvider
@@ -77,30 +78,62 @@ func (f textFilter) Draw(dst draw.Image, src image.Image, options *gift.Options)
 
 	gift.New().Draw(dst, src)
 
-	// Draw text, consider and include linebreaks
 	maxWidth := dst.Bounds().Dx() - 20
+
+	var availableWidth int
+	switch f.alignx {
+	case "right":
+		availableWidth = f.x
+	case "center":
+		availableWidth = min((maxWidth-f.x), f.x) * 2
+	case "left":
+		availableWidth = maxWidth - f.x
+	}
+
 	fontHeight := face.Metrics().Ascent.Ceil()
 
+	// Calculate lines, consider and include linebreaks
+	finalLines := []string{}
+	f.text = strings.ReplaceAll(f.text, "\r", "")
+	for _, line := range strings.Split(f.text, "\n") {
+		currentLine := ""
+		// Break each line at the maximum width.
+		for _, str := range strings.Fields(line) {
+			fieldStrWidth := font.MeasureString(face, str)
+			currentLineStrWidth := font.MeasureString(face, currentLine)
+
+			if (currentLineStrWidth.Ceil() + fieldStrWidth.Ceil()) >= availableWidth {
+				finalLines = append(finalLines, currentLine)
+				currentLine = ""
+			}
+			currentLine += str + " "
+		}
+		finalLines = append(finalLines, currentLine)
+	}
+
 	// Correct y position based on font and size
 	f.y = f.y + fontHeight
 
 	// Start position
 	y := f.y
-	d.Dot = fixed.P(f.x, f.y)
 
-	// Draw text line by line, breaking each line at the maximum width.
-	f.text = strings.ReplaceAll(f.text, "\r", "")
-	for _, line := range strings.Split(f.text, "\n") {
-		for _, str := range strings.Fields(line) {
-			strWidth := font.MeasureString(face, str)
-			if (d.Dot.X.Ceil() + strWidth.Ceil()) >= maxWidth {
-				y = y + fontHeight + f.linespacing
-				d.Dot = fixed.P(f.x, y)
-			}
-			d.DrawString(str + " ")
+	// Draw text line by line
+	for _, line := range finalLines {
+		line = strings.TrimSpace(line)
+		strWidth := font.MeasureString(face, line)
+		var x int
+		switch f.alignx {
+		case "right":
+			x = f.x - strWidth.Ceil()
+		case "center":
+			x = f.x - (strWidth.Ceil() / 2)
+
+		case "left":
+			x = f.x
 		}
+		d.Dot = fixed.P(x, y)
+		d.DrawString(line)
 		y = y + fontHeight + f.linespacing
-		d.Dot = fixed.P(f.x, y)
 	}
 }