Use theme color for textbox cursor and fix #4947

- Change the colors of the background and borders of the textbox to ensure they always contrast with each other
- Make the color of the textbox cursor the same as the skin's text color - this ensure it always has good contrast
- Offset the display of text slightly in the textbox. This avoids the cursor 'blending in' with the textbox border

data/skins/coal/stkskin.xml

@@ -338,12 +338,12 @@ to specify all types of ttf.
 <color type="tips_background" state="neutral" a="120" r="0" g="0" b="0" />
 
 <!-- Text field color -->
-<color type="text_field" state="background" a="255" r="35" g="35" b="35" />
+<color type="text_field" state="background" a="255" r="50" g="50" b="50" />
 <color type="text_field" state="background_focused" a="255" r="15" g="15" b="15" />
-<color type="text_field" state="background_deactivated" a="255" r="90" g="90" b="90" />
+<color type="text_field" state="background_deactivated" a="255" r="120" g="120" b="120" />
 <color type="text_field" state="background_marked" a="128" r="220" g="220" b="220" />
-<color type="text_field" state="neutral" a="255" r="35" g="35" b="35" />
-<color type="text_field" state="focused" a="255" r="15" g="15" b="15" />
+<color type="text_field" state="neutral" a="255" r="20" g="20" b="20" />
+<color type="text_field" state="focused" a="255" r="235" g="235" b="235" />
 <color type="text_field" state="deactivated" a="255" r="90" g="90" b="90" />
 
 <!-- Rating star image -->

src/guiengine/skin.cpp

@@ -2918,7 +2918,15 @@ u32 Skin::getIcon (EGUI_DEFAULT_ICON icon) const
 
 s32 Skin::getSize (EGUI_DEFAULT_SIZE texture_size) const
 {
-    return m_fallback_skin->getSize(texture_size);
+    switch(texture_size)
+    {
+        // TODO : make this depend on the text-size parameter and/or skin
+        // and perhaps rename it
+        case EGDS_TEXT_DISTANCE_X:
+            return 10;
+        default:
+            return m_fallback_skin->getSize(texture_size);
+    }
 }
 
 // -----------------------------------------------------------------------------

src/guiengine/widgets/CGUIEditBox.cpp

@@ -1017,7 +1017,7 @@ void CGUIEditBox::draw()
         core::rect< s32 > caret_rect = CurrentTextRect;
         caret_rect.UpperLeftCorner.X += m_cursor_distance - 1;
         caret_rect.LowerRightCorner.X = caret_rect.UpperLeftCorner.X + 2;
-        GL32_draw2DRectangle(video::SColor(255, 0, 0, 0), caret_rect);
+        GL32_draw2DRectangle(skin->getColor(EGDC_BUTTON_TEXT), caret_rect);
     }
 
     // Return the override color information to its previous settings.