Some small helpers to draw strings and sprites dealing with left-to-right/right-to-left.

src/gfx.cpp

@@ -1592,3 +1592,104 @@ void SortResolutions(int count)
 {
 	QSortT(_resolutions, count, &compare_res);
 }
+
+
+/**
+ * Returns the initial value for a margin, after telling where are the left and right margins and where we want to draw/write (begining/end of line)
+ * @param left is the left margin of the horizontal space we want to draw to
+ * @param right: right margin
+ * @param to_end_line: 0 if working at the begining of the line, 1 if working at the end
+ * @return the margin we asked
+ */
+int InitTempMargin(int left, int right, bool to_end_line)
+{
+	return to_end_line ^ (_current_text_dir == TD_RTL) ? right :left;
+}
+
+/**
+ * Consumes a space in an horizontal margin
+ * @param space: amount of space used
+ * @param here: the margin where to add the space
+ * @param to_end_line: 0 if working at the begining of the line, 1 if working at the end
+ */
+void AddSpace(int space, int &here, bool to_end_line)
+{
+	here += to_end_line ^ (_current_text_dir == TD_RTL) ? -space : space;
+}
+
+/**
+ * After drawing something, update a margin
+ * @param end is where we ended drawing (usually the return value of a DrawString function)
+ * @param margin is the margin we want to update
+ * @param to_end_line: 0 if working at the begining of the line, 1 if working at the end
+ */
+void UpdateMarginEnd(int end, int &margin, bool to_end_line)
+{
+	margin = to_end_line ^ (_current_text_dir == TD_RTL) ? min(end, margin) : max(end, margin);
+}
+
+/**
+ * After drawing something, horizontal margins are updated
+ * @param end: last position drawn
+ * @param left is the left margin of the horizontal space drawn
+ * @param right: right margin
+ * @param to_end_line: 0 if working at the begining of the line, 1 if working at the end
+ */
+void UpdateMarginsEnd(int end, int &left, int &right, bool to_end_line)
+{
+	if (to_end_line ^ (_current_text_dir == TD_RTL)) {
+		right = end;
+	} else {
+		left = end;
+	}
+}
+
+/**
+ * After drawing something of a certain width, update margins
+ * @param width: used space
+ * @param initial left margin
+ * @param initial right margin
+ * @param to_end_line: 0 if working at the begining of the line, 1 if working at the end
+ */
+void UpdateMarginsWidth(int width, int &left, int &right, bool to_end_line)
+{
+	if (to_end_line ^ (_current_text_dir == TD_RTL)) {
+		right -= width;
+	} else {
+		left += width;
+	}
+}
+
+/**
+ * Draws a string in a delimited space; temporal margin gets updated
+ * @param left is the left margin of the horizontal space we want to draw to
+ * @param right: right margin of the horizontal space we want to draw to
+ * @param top: vertical position
+ * @param margin keeps the most extreme limit used of the line (this should be previously initialized with InitTempLimit)
+ * @param string to draw
+ * @param colour for the string
+ * @param alignment of the string (only left or right alignment)
+ * @param underline
+ */
+void DrawString2(int left, int right, int top, int &margin, StringID str, TextColour colour, StringAlignment align, bool underline)
+{
+	int end = DrawString(left, right, top, str, colour, align, underline);
+	UpdateMarginEnd(end, margin, align == SA_RIGHT);
+}
+
+/**
+ * Draws a sprite in a delimited space; temporal margin gets updated
+ * @param width of the sprite
+ * @param left is the left margin of the horizontal space we want to draw to
+ * @param right: right margin of the horizontal space
+ * @param top: vertical position
+ * @param margin keeps the most extreme limit used of the line (this should be previously initialized with InitTempLimit)
+ * @param sprite
+ * @param palette
+ * @param to_end_line: 0 if working at the begining of the line, 1 if working at the end
+ */
+void DrawSprite2(int width, int left, int right, int top, int &margin, SpriteID img, PaletteID pal, bool to_end_line, SubSprite *sub)
+{
+	DrawSprite(img, pal, to_end_line ^ (_current_text_dir == TD_RTL) ? right - width : left, top, sub);
+	margin = to_end_line ^ (_current_text_dir == TD_RTL) ? min(right - width, margin): max(margin, left + width);
+}