Add disabled effect for Stone themed buttons and Modern themed checkboxes. Patch by Imarok, fixes #4165.

This was SVN commit r18639.

binaries/data/mods/mod/gui/common/modern/sprites.xml

@@ -769,13 +769,20 @@
 			size="0 0 22 22"
 		/>
 	</sprite>
-	<sprite name="ModernTickDisabled">
+	<sprite name="ModernTickDisabledOn">
 		<effect grayscale=""/>
 		<image texture="global/modern/tick-on.png"
 			real_texture_placement="0 0 27 27"
 			size="0 0 22 22"
 		/>
 	</sprite>
+	<sprite name="ModernTickDisabledOff">
+		<effect	add_color="35 35 35 0"/>
+		<image texture="global/modern/tick-off.png"
+			real_texture_placement="0 0 27 27"
+			size="0 0 22 22"
+		/>
+	</sprite>
 	<sprite name="ModernGear">
 		<image texture="global/modern/gear.png"
 			texture_size="0 0 24 24"

binaries/data/mods/mod/gui/common/modern/styles.xml

@@ -128,8 +128,8 @@
 	<style name="ModernTickBox"
 		sprite="ModernTickOff"
 		sprite2="ModernTickOn"
-		sprite_disabled="ModernTickDisabled"
-		sprite2_disabled="ModernTickDisabled"
+		sprite_disabled="ModernTickDisabledOff"
+		sprite2_disabled="ModernTickDisabledOn"
 		square_side="22"
 		sound_pressed="audio/interface/ui/ui_button_click.ogg"
 	/>

binaries/data/mods/public/gui/common/sprites.xml

@@ -259,7 +259,7 @@
         </sprite>
 
 	<sprite name="StoneButtonDisabled">
-		<effect grayscale="" />
+		<effect add_color="42 42 42 0"/>
 		<image 	texture="global/button/button_stone_unselected.png"
 			real_texture_placement="0 0 256 28"
 			size="0 0 100% 100%"