gui: keyboard: support longpress label offset, code cleanup

To position the longpress label:
<longpress font="..." textcolor="..." x="5" y="0"/>
x and y is the distance from the upper right corner.

- extract method GUIKeyboard::DrawKey
- clean up handling of currently pressed key
- integrate key highlighting into main key drawing loops

Change-Id: I80ccf2975d30cffa2a48627a74ab3693c84e4fa4

gui/objects.hpp

@@ -853,6 +853,7 @@ protected:
 	};
 	int ParseKey(const char* keyinfo, Key& key, int& Xindex, int keyWidth, bool longpress);
 	void LoadKeyLabels(xml_node<>* parent, int layout);
+	void DrawKey(Key& key, int keyX, int keyY, int keyW, int keyH);
 
 	enum {
 		MAX_KEYBOARD_LAYOUTS = 5,
@@ -886,7 +887,8 @@ protected:
 	std::string mVariable;
 	int currentLayout;
 	bool CapsLockOn;
-	int rowY, colX, highlightRenderCount;
+	int highlightRenderCount;
+	Key* currentKey;
 	bool hasHighlight, hasCapsHighlight;
 	COLOR mHighlightColor;
 	COLOR mCapsHighlightColor;
@@ -895,6 +897,7 @@ protected:
 	FontResource* mFont; // for main key labels
 	FontResource* mSmallFont; // for key labels like "?123"
 	FontResource* mLongpressFont; // for the small longpress label in the upper right corner
+	int longpressOffsetX, longpressOffsetY; // distance of the longpress label from the key corner
 	COLOR mLongpressFontColor;
 	COLOR mBackgroundColor; // keyboard background color
 	COLOR mKeyColorAlphanumeric; // key background color