Implement stylesheet config option

Thanks to thorsten!

doc/katarakt.txt

@@ -181,6 +181,21 @@ VARIABLES
 	katarakt instance, then the other katarakt window is activated instead.
 'string' *icon_theme* ::
 	The name of your icon theme. Fill in if auto detection fails.
+'string' *stylesheet* ::
+	See link:http://doc.qt.io/qt-4.8/stylesheet.html[]. It can be overridden
+	via Qt's *-stylesheet* command line option. The following example changes
+	the 'goto page' bar: +
++
+----
+stylesheet="
+GotoLine {
+	margin: 0px;
+	padding: 4px;
+	border-top-right-radius: 6px;
+	border-top: 1px solid black;
+	border-right: 1px solid black;
+}"
+----
 
 'int' *click_link_button* ::
 	1: The mouse button used for clicking links. Buttons 1-5 are supported.

share/katarakt.ini

@@ -18,6 +18,7 @@ thumbnail_size=32
 rect_expansion=2
 quit_on_init_fail=false
 icon_theme=
+stylesheet=
 click_link_button=1
 drag_view_button=2
 select_text_button=1

src/config.cpp

@@ -42,6 +42,7 @@ void CFG::init_defaults() {
 	defaults["quit_on_init_fail"] = false;
 	defaults["single_instance_per_file"] = false;
 	defaults["icon_theme"] = "";
+	defaults["stylesheet"] = "";
 
 	// mouse buttons
 	defaults["click_link_button"] = 1;

src/main.cpp

@@ -111,6 +111,11 @@ int main(int argc, char *argv[]) {
 		}
 	}
 
+	// load stylesheet from config if no stylesheet was specified on the command line
+	if (app.styleSheet().isEmpty()) {
+		app.setStyleSheet(CFG::get_instance()->get_value("stylesheet").toString());
+	}
+
 	Viewer katarakt(file);
 	if (!katarakt.is_valid()) {
 		return 1;