Codechange: Simplify calling of DrawCharCentered()

(cherry picked from commit 2efa390a7d)

src/gfx.cpp

@@ -910,15 +910,17 @@ const char *GetCharAtPosition(const char *str, int x, FontSize start_fontsize)
 /**
  * Draw single character horizontally centered around (x,y)
  * @param c           Character (glyph) to draw
- * @param x           X position to draw character
- * @param y           Y position to draw character
+ * @param r           Rectangle to draw character within
  * @param colour      Colour to use, for details see _string_colourmap in
  *                    table/palettes.h or docs/ottd-colourtext-palette.png or the enum TextColour in gfx_type.h
  */
-void DrawCharCentered(WChar c, int x, int y, TextColour colour)
+void DrawCharCentered(WChar c, const Rect &r, TextColour colour)
 {
 	SetColourRemap(colour);
-	GfxMainBlitter(GetGlyph(FS_NORMAL, c), x - GetCharacterWidth(FS_NORMAL, c) / 2, y, BM_COLOUR_REMAP);
+	GfxMainBlitter(GetGlyph(FS_NORMAL, c),
+		CenterBounds(r.left, r.right, GetCharacterWidth(FS_NORMAL, c)),
+		CenterBounds(r.top, r.bottom, FONT_HEIGHT_NORMAL),
+		BM_COLOUR_REMAP);
 }
 
 /**

src/gfx_func.h

@@ -97,7 +97,7 @@ int DrawString(int left, int right, int top, StringID str, TextColour colour = T
 int DrawStringMultiLine(int left, int right, int top, int bottom, const char *str, TextColour colour = TC_FROMSTRING, StringAlignment align = (SA_TOP | SA_LEFT), bool underline = false, FontSize fontsize = FS_NORMAL);
 int DrawStringMultiLine(int left, int right, int top, int bottom, StringID str, TextColour colour = TC_FROMSTRING, StringAlignment align = (SA_TOP | SA_LEFT), bool underline = false, FontSize fontsize = FS_NORMAL);
 
-void DrawCharCentered(WChar c, int x, int y, TextColour colour);
+void DrawCharCentered(WChar c, const Rect &r, TextColour colour);
 
 void GfxFillRect(int left, int top, int right, int bottom, int colour, FillRectMode mode = FILLRECT_OPAQUE);
 void GfxFillPolygon(const std::vector<Point> &shape, int colour, FillRectMode mode = FILLRECT_OPAQUE);

src/osk_gui.cpp

@@ -103,10 +103,7 @@ struct OskWindow : public Window {
 		if (widget < WID_OSK_LETTERS) return;
 
 		widget -= WID_OSK_LETTERS;
-		DrawCharCentered(_keyboard[this->shift][widget],
-			r.left + (r.right - r.left) / 2,
-			r.top + (r.bottom - r.top - FONT_HEIGHT_NORMAL) / 2,
-			TC_BLACK);
+		DrawCharCentered(_keyboard[this->shift][widget], r, TC_BLACK);
 	}
 
 	void OnClick(Point pt, int widget, int click_count) override