ui: Use window decorations on dialog windows (issue #376)

* added SubWindow flag to QtWindow to either use window decorations or show window within main window
* fixes black borders in some Linux window managers

bug id = 376

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bin/app/data/gui/about/about.css

@@ -4,16 +4,6 @@
 	font-weight: 100;
 }
 
-#closeButton {
-	background: transparent;
-	border: none;
-	color: white;
-	font-size: 14px;
-	height: 24px;
-	width: 24px;
-}
-
-#closeButton:hover {
-	border: 2px solid white;
-	border-radius: 12px;
+#window {
+	background: qlineargradient( x1:0 y1:0.4, x2:0 y2:1, stop:0 #2F3F86, stop:1 #1C7BBC );
 }

bin/app/data/gui/bookmark_view/bookmark_view.css

@@ -2,8 +2,6 @@
 
 #header_background {
 	background-color: #2E3C86;
-	border-top-left-radius: 15px;
-	border-bottom-left-radius: 15px;
 }
 
 #title {
@@ -142,8 +140,6 @@
 
 #creator_header_background {
 	background-color: #2E3C86;
-	border-top-left-radius: 15px;
-	border-top-right-radius: 15px;
 }
 
 #creator_title_label {

bin/app/data/gui/license/license.css

@@ -1,8 +1,3 @@
-QLabel {
-	font-size: 12px;
-	color: black;
-}
-
 #licenseField {
 	font-family: "<setting:font_name>";
 	font-size: 11px;

bin/app/data/gui/window/window.css

@@ -14,6 +14,10 @@ QCheckBox:disabled {
 	color: gray;
 }
 
+#window {
+	background: white;
+}
+
 #title {
 	font-size: 16px;
 	font-weight: bold;