Bug 462009 - [Gtk3] Button background Color fix (Patch 2)

Tests:
All SWT Button styles *:
 - [X] Gtk 3.8  (RHEL 7 native)
 - [X] Gtk 3.10 (F21, manual gtk compile)
 - [X] Gtk 3.12 (F21, manual gtk compile)
 - [X] Gtk 3.14 (F21, native gtk)
 - [X] Gtk 3.15.11 (F22, native)

This corrects the issue that checkbox/radiobutton is not visible when
background is applied for some themes (gtk unstyled, ubuntu etc..).

Change-Id: I1d1091b5d949ef153cb7db07e44034a2d2d4dcf2
Signed-off-by: Leo Ufimtsev <lufimtse@redhat.com>

2 files changed, 41 insertions, 6 deletions

diff --git a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Button.java b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Button.java
index d5437aa5cb..8fd50580c9 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Button.java
+++ b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Button.java
@@ -11,11 +11,11 @@
 package org.eclipse.swt.widgets;
 
 
-import org.eclipse.swt.internal.*;
-import org.eclipse.swt.internal.gtk.*;
 import org.eclipse.swt.*;
-import org.eclipse.swt.graphics.*;
 import org.eclipse.swt.events.*;
+import org.eclipse.swt.graphics.*;
+import org.eclipse.swt.internal.*;
+import org.eclipse.swt.internal.gtk.*;
 
 /**
  * Instances of this class represent a selectable user interface object that
@@ -796,8 +796,23 @@ void _setAlignment (int alignment) {
 }
 
 @Override
-void setBackgroundColor (long /*int*/ context, long /*int*/ handle, GdkRGBA rgba) { //Gtk3.
-	setBackgroundColorGradient (OS.gtk_widget_get_style_context (handle), handle, rgba);
+void setBackgroundColor (long /*int*/ context, long /*int*/ handle, GdkRGBA rgba) {
+	/* Note: this function is called on Gtk3 only */
+
+	//Pre Gtk 3.10 doesn't handle CSS background color very well for Gtk Check/Radio button.
+	// 3.10.3 as it was the latest to affect themeing in button.
+	if (OS.GTK_VERSION < OS.VERSION(3, 10, 3) && (style & (SWT.CHECK | SWT.RADIO)) != 0) {
+		super.setBackgroundColor (context, handle, rgba);
+		return;
+	}
+
+	String css ="* {\n";
+	if (rgba != null) {
+		String color = gtk_rgba_to_css_string (rgba);
+		css += "background: " + color + ";\n";
+	}
+	css += "}\n";
+	gtk_css_provider_load_from_css (context, css);
 }
 
 @Override
diff --git a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Control.java b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Control.java
index ac80045ed8..701d6756b9 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Control.java
+++ b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Control.java
@@ -4086,10 +4086,19 @@ void setBackgroundColor (long /*int*/ context, long /*int*/ handle, GdkRGBA rgba
 void setBackgroundColorGradient (long /*int*/ context, long /*int*/ handle, GdkRGBA rgba) {
 	String css ="* {\n";
 	if (rgba != null) {
-		String color = "rgba(" + (int)(rgba.red * 255) + "," + (int)(rgba.green * 255) + "," + (int)(rgba.blue * 255) + "," + (int)(rgba.alpha * 255) + ")";
+		String color = gtk_rgba_to_css_string (rgba);
+		//Note, use 'background-image' CSS class with caution. Not all themes/widgets support it. (e.g button doesn't).
+		//Use 'background' CSS class where possible instead unless 'background-image' is explicidly supported.
 		css += "background-image: -gtk-gradient (linear, 0 0, 0 1, color-stop(0, " + color + "), color-stop(1, " + color + "));\n";
 	}
 	css += "}\n";
+	gtk_css_provider_load_from_css (context, css);
+}
+
+void gtk_css_provider_load_from_css (long context, String css) {
+	/* Utility function. */
+	//@param css : a 'css java' string like "{\nbackground: red;\n}".
+
 	if (provider == 0) {
 		provider = OS.gtk_css_provider_new ();
 		OS.gtk_style_context_add_provider (context, provider, OS.GTK_STYLE_PROVIDER_PRIORITY_APPLICATION);
@@ -4098,6 +4107,17 @@ void setBackgroundColorGradient (long /*int*/ context, long /*int*/ handle, GdkR
 	OS.gtk_css_provider_load_from_data (provider, Converter.wcsToMbcs (null, css, true), -1, null);
 }
 
+String gtk_rgba_to_css_string (GdkRGBA rgba) {
+	/*
+	 * In GdkRGBA, values are a double between 0-1.<br>
+     * In CSS, values are typically integers between 0-255.<br>
+     * I.e, note, there is a slight loss of precision.
+     * Thus setting/getting color *might* return slight differences.
+	 */
+	String color = "rgba(" + (int)(rgba.red * 255) + "," + (int)(rgba.green * 255) + "," + (int)(rgba.blue * 255) + "," + (int)(rgba.alpha * 255) + ")";
+	return color;
+}
+
 void setBackgroundColor (long /*int*/ handle, GdkColor color) {
 	if (OS.GTK3) {
 		GdkRGBA rgba = null;