GButton: Align the button text according to text_alignment().

Added a Rect::align_within(other_rect, alignment) helper that seemed useful.

LibGUI/GButton.cpp

@@ -52,8 +52,8 @@ void GButton::paint_event(GPaintEvent& event)
     Rect text_rect { 0, 0, font.width(text()), font.glyph_height() };
     if (text_rect.width() > content_rect.width())
         text_rect.set_width(content_rect.width());
-    text_rect.center_within(content_rect);
+    text_rect.align_within(content_rect, text_alignment());
-    paint_text(painter, text_rect, font, text_alignment());
+    paint_text(painter, text_rect, font, TextAlignment::Center);
 }
 
 void GButton::click()

SharedGraphics/Rect.cpp

@@ -76,3 +76,23 @@ Vector<Rect> Rect::shatter(const Rect& hammer) const
 
     return pieces;
 }
+
+void Rect::align_within(const Rect& other, TextAlignment alignment)
+{
+    switch (alignment) {
+    case TextAlignment::Center:
+        center_within(other);
+        return;
+    case TextAlignment::TopLeft:
+        set_location(other.location());
+        return;
+    case TextAlignment::CenterLeft:
+        set_x(other.x());
+        center_vertically_within(other);
+        return;
+    case TextAlignment::CenterRight:
+        set_x(other.x() + other.width() - width());
+        center_vertically_within(other);
+        return;
+    }
+}

SharedGraphics/Rect.h

@@ -1,8 +1,9 @@
 #pragma once
 
-#include "Point.h"
-#include "Size.h"
 #include <AK/AKString.h>
+#include <SharedGraphics/Point.h>
+#include <SharedGraphics/Size.h>
+#include <SharedGraphics/TextAlignment.h>
 
 struct WSAPI_Rect;
 
@@ -207,6 +208,8 @@ public:
     Point bottom_left() const { return { left(), bottom() }; }
     Point bottom_right() const { return { right(), bottom() }; }
 
+    void align_within(const Rect&, TextAlignment);
+
     void center_within(const Rect& other)
     {
         center_horizontally_within(other);