Use WebViewLifetimeListener in WebControlRelays

BREAKING_CHANGES.md

@@ -2,6 +2,32 @@
 
 # develop
 
+## Change
+
+The constructors of the WebSliderRelay, WebToggleButtonRelay and 
+WebComboBoxRelay classes were changed and they no longer accept a reference
+parameter to a WebBrowserComponent object.
+
+**Possible Issues**
+
+Code that uses these classes will fail to compile.
+
+**Workaround**
+
+Omit the WebBrowserComponent parameter when constructing the relay objects.
+
+**Rationale**
+
+The relay classes use a new underlying mechanism to obtain a pointer to the
+WebBrowserComponent object. When calling the
+WebBrowserComponent::Options::withOptionsFrom() function with the relay as a
+parameter, the corresponding WebBrowserComponent object will notify the relay
+about its creation and destruction.
+
+This avoids the anti-pattern where the relay class required a reference to a
+yet uninitialised WebBrowserComponent object.
+
+
 ## Change
 
 The coefficients of LadderFilter::Mode::BPF12 have been changed, causing a

examples/Plugins/WebViewPluginDemo.h

@@ -438,9 +438,9 @@ public:
 private:
     WebViewPluginAudioProcessor& processorRef;
 
-    WebSliderRelay       cutoffSliderRelay    { webComponent, "cutoffSlider" };
+    WebSliderRelay       cutoffSliderRelay    { "cutoffSlider" };
-    WebToggleButtonRelay muteToggleRelay      { webComponent, "muteToggle" };
+    WebToggleButtonRelay muteToggleRelay      { "muteToggle" };
-    WebComboBoxRelay     filterTypeComboRelay { webComponent, "filterTypeCombo" };
+    WebComboBoxRelay     filterTypeComboRelay { "filterTypeCombo" };
 
     WebControlParameterIndexReceiver controlParameterIndexReceiver;
 

modules/juce_gui_extra/misc/juce_WebControlRelays.cpp

@@ -37,9 +37,8 @@ namespace juce
 
 #if JUCE_WEB_BROWSER
 
-WebSliderRelay::WebSliderRelay (WebBrowserComponent& browserIn, StringRef nameIn)
+WebSliderRelay::WebSliderRelay (StringRef nameIn)
-    : browser (browserIn),
+    : name (nameIn)
-      name (nameIn)
 {
 }
 
@@ -75,12 +74,25 @@ WebBrowserComponent::Options WebSliderRelay::buildOptions (const WebBrowserCompo
 {
     return initialOptions
         .withEventListener (eventId, [this] (auto object) { handleEvent (object); })
-        .withInitialisationData ("__juce__sliders", name);
+        .withInitialisationData ("__juce__sliders", name)
+        .withWebViewLifetimeListener (this);
 }
 
 void WebSliderRelay::emitEvent (const var& payload)
 {
-    browser.emitEventIfBrowserIsVisible (eventId, payload);
+    if (browser != nullptr)
+        browser->emitEventIfBrowserIsVisible (eventId, payload);
+}
+
+void WebSliderRelay::webViewConstructed (WebBrowserComponent* browserIn)
+{
+    browser = browserIn;
+    listeners.call (&Listener::initialUpdateRequested, this);
+}
+
+void WebSliderRelay::webViewDestructed (WebBrowserComponent*)
+{
+    browser = nullptr;
 }
 
 void WebSliderRelay::handleEvent (const var& event)
@@ -122,9 +134,8 @@ void WebSliderRelay::handleEvent (const var& event)
 }
 
 //==============================================================================
-WebToggleButtonRelay::WebToggleButtonRelay ([[maybe_unused]] WebBrowserComponent& browserIn, StringRef nameIn)
+WebToggleButtonRelay::WebToggleButtonRelay (StringRef nameIn)
-    : browser (browserIn),
+    : name (nameIn)
-      name (nameIn)
 {
 }
 
@@ -154,12 +165,25 @@ WebBrowserComponent::Options WebToggleButtonRelay::buildOptions (const WebBrowse
 {
     return initialOptions
               .withEventListener (eventId, [this] (auto object) { handleEvent (object); })
-              .withInitialisationData ("__juce__toggles", name);
+              .withInitialisationData ("__juce__toggles", name)
+              .withWebViewLifetimeListener (this);
 }
 
 void WebToggleButtonRelay::emitEvent (const var& payload)
 {
-    browser.emitEventIfBrowserIsVisible (eventId, payload);
+    if (browser != nullptr)
+        browser->emitEventIfBrowserIsVisible (eventId, payload);
+}
+
+void WebToggleButtonRelay::webViewConstructed (WebBrowserComponent* browserIn)
+{
+    browser = browserIn;
+    listeners.call (&Listener::initialUpdateRequested);
+}
+
+void WebToggleButtonRelay::webViewDestructed (WebBrowserComponent*)
+{
+    browser = nullptr;
 }
 
 void WebToggleButtonRelay::handleEvent (const var& event)
@@ -187,9 +211,8 @@ void WebToggleButtonRelay::handleEvent (const var& event)
 }
 
 //==============================================================================
-WebComboBoxRelay::WebComboBoxRelay ([[maybe_unused]] WebBrowserComponent& browserIn, StringRef nameIn)
+WebComboBoxRelay::WebComboBoxRelay (StringRef nameIn)
-    : browser (browserIn),
+    : name (nameIn)
-      name (nameIn)
 {
 }
 
@@ -219,12 +242,25 @@ WebBrowserComponent::Options WebComboBoxRelay::buildOptions (const WebBrowserCom
 {
     return initialOptions
         .withEventListener (eventId, [this] (auto object) { handleEvent (object); })
-        .withInitialisationData ("__juce__comboBoxes", name);
+        .withInitialisationData ("__juce__comboBoxes", name)
+        .withWebViewLifetimeListener (this);
 }
 
 void WebComboBoxRelay::emitEvent (const var& payload)
 {
-    browser.emitEventIfBrowserIsVisible (eventId, payload);
+    if (browser != nullptr)
+        browser->emitEventIfBrowserIsVisible (eventId, payload);
+}
+
+void WebComboBoxRelay::webViewConstructed (WebBrowserComponent* browserIn)
+{
+    browser = browserIn;
+    listeners.call (&Listener::initialUpdateRequested);
+}
+
+void WebComboBoxRelay::webViewDestructed (WebBrowserComponent*)
+{
+    browser = nullptr;
 }
 
 void WebComboBoxRelay::handleEvent (const var& event)

modules/juce_gui_extra/misc/juce_WebControlRelays.h

@@ -62,14 +62,15 @@ namespace juce
 
     @tags{GUI}
 */
-class JUCE_API  WebSliderRelay : public OptionsBuilder<WebBrowserComponent::Options>
+class JUCE_API  WebSliderRelay : public OptionsBuilder<WebBrowserComponent::Options>,
+                                 private WebViewLifetimeListener
 {
 public:
     /** Creating a relay will ensure that a Javascript object under the provided name will be
         available in the specified WebBrowserComponent's context. Use the frontend framework's
         getSliderState function with the same name to get a hold of this object.
     */
-    WebSliderRelay (WebBrowserComponent& browserIn, StringRef nameIn);
+    WebSliderRelay (StringRef nameIn);
 
     //==============================================================================
     /** @internal */
@@ -98,8 +99,10 @@ public:
 
 private:
     void handleEvent (const var& event);
+    void webViewConstructed (WebBrowserComponent*) override;
+    void webViewDestructed (WebBrowserComponent*) override;
 
-    WebBrowserComponent& browser;
+    WebBrowserComponent* browser = nullptr;
     String name;
     float value{};
     Identifier eventId { "__juce__slider" + name };
@@ -134,14 +137,15 @@ private:
 
     @tags{GUI}
 */
-class JUCE_API  WebToggleButtonRelay  : public OptionsBuilder<WebBrowserComponent::Options>
+class JUCE_API  WebToggleButtonRelay  : public OptionsBuilder<WebBrowserComponent::Options>,
+                                        private WebViewLifetimeListener
 {
 public:
     /** Creating a relay will ensure that a Javascript object under the provided name will be
         available in the specified WebBrowserComponent's context. Use the frontend framework's
         getToggleState function with the same name to get a hold of this object.
     */
-    WebToggleButtonRelay (WebBrowserComponent& browserIn, StringRef nameIn);
+    WebToggleButtonRelay (StringRef nameIn);
 
     //==============================================================================
     /** @internal */
@@ -169,8 +173,10 @@ public:
 
 private:
     void handleEvent (const var& event);
+    void webViewConstructed (WebBrowserComponent*) override;
+    void webViewDestructed (WebBrowserComponent*) override;
 
-    WebBrowserComponent& browser;
+    WebBrowserComponent* browser = nullptr;
     String name;
     Identifier eventId { "__juce__toggle" + name };
     ListenerList<Listener> listeners;
@@ -204,14 +210,15 @@ private:
 
     @tags{GUI}
 */
-class JUCE_API  WebComboBoxRelay  : public OptionsBuilder<WebBrowserComponent::Options>
+class JUCE_API  WebComboBoxRelay  : public OptionsBuilder<WebBrowserComponent::Options>,
+                                    private WebViewLifetimeListener
 {
 public:
     /** Creating a relay will ensure that a Javascript object under the provided name will be
         available in the specified WebBrowserComponent's context. Use the frontend framework's
         getComboBoxState function with the same name to get a hold of this object.
     */
-    WebComboBoxRelay (WebBrowserComponent& browserIn, StringRef nameIn);
+    WebComboBoxRelay (StringRef nameIn);
 
     //==============================================================================
     /** @internal */
@@ -239,8 +246,10 @@ public:
 
 private:
     void handleEvent (const var& event);
+    void webViewConstructed (WebBrowserComponent*) override;
+    void webViewDestructed (WebBrowserComponent*) override;
 
-    WebBrowserComponent& browser;
+    WebBrowserComponent* browser = nullptr;
     String name;
     Identifier eventId { "__juce__comboBox" + name };
     ListenerList<Listener> listeners;