Adds opacity slider option to color panel (#155)

Adds opacity slider option to color panel

Author: franciscojma86

plugins/color_panel/common/channel_constants.cc

@@ -18,6 +18,7 @@ namespace plugins_color_panel {
 const char kChannelName[] = "flutter/colorpanel";
 
 const char kShowColorPanelMethod[] = "ColorPanel.Show";
+const char kColorPanelShowAlpha[] = "ColorPanel.ShowAlpha";
 const char kHideColorPanelMethod[] = "ColorPanel.Hide";
 const char kColorSelectedCallbackMethod[] = "ColorPanel.ColorSelectedCallback";
 const char kClosedCallbackMethod[] = "ColorPanel.ClosedCallback";

plugins/color_panel/common/channel_constants.h

@@ -32,6 +32,9 @@ extern const char kColorSelectedCallbackMethod[];
 // closed from the UI, rather than via a call to kHideColorPanelMethod.
 extern const char kClosedCallbackMethod[];
 
+// The argument to show an opacity modifier on the panel. Default is true.
+extern const char kColorPanelShowAlpha[];
+
 // Keys for the RGB color JSON object sent to kColorPanelCallback.
 // The values should be numbers between 0 and 1.
 extern const char kColorComponentRedKey[];

plugins/color_panel/lib/color_panel.dart

@@ -23,6 +23,7 @@ const String _kHideColorPanelMethod = 'ColorPanel.Hide';
 const String _kColorPanelColorSelectedCallback =
     'ColorPanel.ColorSelectedCallback';
 const String _kColorPanelClosedCallback = 'ColorPanel.ClosedCallback';
+const String _kColorPanelShowAlpha = 'ColorPanel.ShowAlpha';
 const String _kRedKey = 'red';
 const String _kGreenKey = 'green';
 const String _kBlueKey = 'blue';
@@ -55,14 +56,15 @@ class ColorPanel {
   ///
   /// [callback] will be called when the user selects a color; it can be called
   /// an number of times depending on the interaction model of the native
-  /// panel.
+  /// panel. Set [showAlpha] to false to hide the color opacity modifier UI.
   ///
   /// It is an error to call [show] if the panel is already showing.
-  void show(ColorPanelCallback callback) {
+  void show(ColorPanelCallback callback, {bool showAlpha = true}) {
     try {
       if (!showing) {
         _callback = callback;
-        _platformChannel.invokeMethod(_kShowColorPanelMethod);
+        _platformChannel.invokeMethod(_kShowColorPanelMethod,
+            {_kColorPanelShowAlpha: showAlpha});
       } else {
         throw new StateError('Color panel is already shown');
       }

plugins/color_panel/linux/src/color_panel_plugin.cc

@@ -29,8 +29,12 @@ using flutter_desktop_embedding::MethodResult;
 // This is to avoid having the user import extra GTK headers.
 class ColorPanelPlugin::ColorPanel {
  public:
-  explicit ColorPanel(ColorPanelPlugin *parent) {
+  explicit ColorPanel(ColorPanelPlugin *parent,
+                      const Json::Value &method_args) {
     gtk_widget_ = gtk_color_chooser_dialog_new(kWindowTitle, nullptr);
+    gtk_color_chooser_set_use_alpha(
+        reinterpret_cast<GtkColorChooser *>(gtk_widget_),
+        method_args[kColorPanelShowAlpha].asBool());
     gtk_widget_show_all(gtk_widget_);
     g_signal_connect(gtk_widget_, "close", G_CALLBACK(CloseCallback), parent);
     g_signal_connect(gtk_widget_, "response", G_CALLBACK(ResponseCallback),
@@ -99,7 +103,8 @@ void ColorPanelPlugin::HandleJsonMethodCall(
     if (color_panel_) {
       return;
     }
-    color_panel_ = std::make_unique<ColorPanelPlugin::ColorPanel>(this);
+    color_panel_ = std::make_unique<ColorPanelPlugin::ColorPanel>(
+        this, method_call.GetArgumentsAsJson());
   } else if (method_call.method_name().compare(kHideColorPanelMethod) == 0) {
     result->Success();
     if (color_panel_ == nullptr) {

plugins/color_panel/macos/FLEColorPanelPlugin.mm

@@ -33,7 +33,16 @@ - (NSString *)channel {
 - (void)handleMethodCall:(FLEMethodCall *)call result:(FLEMethodResult)result {
   BOOL handled = YES;
   if ([call.methodName isEqualToString:@(plugins_color_panel::kShowColorPanelMethod)]) {
-    [self showColorPanel];
+    if ([call.arguments isKindOfClass:[NSDictionary class]]) {
+      BOOL showAlpha =
+      [[call.arguments valueForKey:@(plugins_color_panel::kColorPanelShowAlpha)] boolValue];
+      [self showColorPanelWithAlpha:showAlpha];
+    } else {
+      NSLog(@"Malformed call for %@. Expected an NSDictionary but got %@",
+            @(plugins_color_panel::kShowColorPanelMethod),
+            NSStringFromClass([call.arguments class]));
+      handled = NO;
+    }
   } else if ([call.methodName isEqualToString:@(plugins_color_panel::kHideColorPanelMethod)]) {
     [self hideColorPanel];
   } else {
@@ -47,9 +56,10 @@ - (void)handleMethodCall:(FLEMethodCall *)call result:(FLEMethodResult)result {
 /**
  * Configures the shared instance of NSColorPanel and makes it the frontmost & key window.
  */
-- (void)showColorPanel {
+- (void)showColorPanelWithAlpha:(BOOL)showAlpha {
   NSColorPanel *sharedColor = [NSColorPanel sharedColorPanel];
   sharedColor.delegate = self;
+  [sharedColor setShowsAlpha:showAlpha];
   [sharedColor setTarget:self];
   [sharedColor setAction:@selector(selectedColorDidChange)];
   if (!sharedColor.isKeyWindow) {