feat: 🎸 React custom component on toolbar button (#935)

* feat: 🎸 React custom component on toolbar button

Toolbar button can consume/render react custom components. Its only
required to expose the component into toolbar definitions
(toolbarModule)

Closes: 924

* feat: 🎸 Core review. Minor changes on documentation

Closes: 924

* feat: 🎸 Code review

* feat: 🎸 Code review. Changing function call to variable decl

docs/latest/advanced/extensions.md

@@ -160,6 +160,7 @@ An extension can register a Toolbar Module by providing a `getToolbarModule()`
 method that returns a React Component. The component does not receive any props.
 If you want to modify or react to state, you will need to connect to the redux
 store.
+The given toolbar must determine its set of elements and the context of them. The set of elements will be listed on toolbar `definitions`.
 
 ![Toolbar Extension](../assets/img/extensions-toolbar.gif)
 
@@ -170,6 +171,31 @@ Toolbar components are rendered in the `ToolbarRow` component.
 For a complete example implementation,
 [check out the OHIFCornerstoneViewport's Toolbar Module](https://github.com/OHIF/Viewers/blob/master/extensions/cornerstone/src/toolbarModule.js).
 
+##### Toolbar Custom Component
+
+Toolbar elements can define its own custom react component to be consumed when rendering it. So far, it accepts `Functional` and `Class` Components. For that, you just need to expose your `CustomToolbarComponent` as the value of key `CustomComponent`. In case the property `CustomComponent` is not present, a default toolbar component will be used to render it. See bellow
+
+```js
+definitions: [
+...
+    {
+        id: 'Custom',
+        label: 'Custom',
+        icon: 'custom-icon',
+        CustomComponent: CustomToolbarComponent,
+    }
+...
+]
+
+```
+`CustomComponent` components will receive the following props:
+- parentContext: parent context. (In most of the cases it will be a ToolbarRow instance)
+- toolbarClickCallback: callback method when clicking on toolbar
+- button: its own definition object
+- key: react key prop
+- activeButtons: list of active elements
+- isActive: if current
+
 #### SopClassHandler
 
 ...

platform/viewer/src/connectedComponents/ToolbarRow.js

@@ -150,45 +150,82 @@ class ToolbarRow extends Component {
   }
 }
 
+function _getCustomButtonComponent(button, activeButtons) {
+  const CustomComponent = button.CustomComponent;
+  const isValidComponent = typeof CustomComponent === 'function';
+
+  // Check if its a valid customComponent. Later on an CustomToolbarComponent interface could be implemented.
+  if (isValidComponent) {
+    const parentContext = this;
+    const isActive = activeButtons.includes(button.id);
+
+    return (
+      <CustomComponent
+        parentContext={parentContext}
+        toolbarClickCallback={_handleToolbarButtonClick.bind(this)}
+        button={button}
+        key={button.id}
+        activeButtons={activeButtons}
+        isActive={isActive}
+      />
+    );
+  }
+}
+
+function _getExpandableButtonComponent(button, activeButtons) {
+  // Iterate over button definitions and update `onClick` behavior
+  let activeCommand;
+  const childButtons = button.buttons.map(childButton => {
+    childButton.onClick = _handleToolbarButtonClick.bind(this, childButton);
+
+    if (activeButtons.indexOf(childButton.id) > -1) {
+      activeCommand = childButton.id;
+    }
+
+    return childButton;
+  });
+
+  return (
+    <ExpandableToolMenu
+      key={button.id}
+      label={button.label}
+      icon={button.icon}
+      buttons={childButtons}
+      activeCommand={activeCommand}
+    />
+  );
+}
+
+function _getDefaultButtonComponent(button, activeButtons) {
+  return (
+    <ToolbarButton
+      key={button.id}
+      label={button.label}
+      icon={button.icon}
+      onClick={_handleToolbarButtonClick.bind(this, button)}
+      isActive={activeButtons.includes(button.id)}
+    />
+  );
+}
 /**
  * Determine which extension buttons should be showing, if they're
  * active, and what their onClick behavior should be.
  */
 function _getButtonComponents(toolbarButtons, activeButtons) {
-  return toolbarButtons.map((button, index) => {
-    let activeCommand = undefined;
+  const _this = this;
+  return toolbarButtons.map(button => {
+    const hasCustomComponent = button.CustomComponent;
+    const hasNestedButtonDefinitions = button.buttons && button.buttons.length;
 
-    if (button.buttons && button.buttons.length) {
-      // Iterate over button definitions and update `onClick` behavior
-      const childButtons = button.buttons.map(childButton => {
-        childButton.onClick = _handleToolbarButtonClick.bind(this, childButton);
-
-        if (activeButtons.indexOf(childButton.id) > -1) {
-          activeCommand = childButton.id;
-        }
-
-        return childButton;
-      });
-
-      return (
-        <ExpandableToolMenu
-          key={button.id}
-          label={button.label}
-          icon={button.icon}
-          buttons={childButtons}
-          activeCommand={activeCommand}
-        />
-      );
+    if (hasCustomComponent) {
+      return _getCustomButtonComponent.call(_this, button, activeButtons);
     }
-    return (
-      <ToolbarButton
-        key={button.id}
-        label={button.label}
-        icon={button.icon}
-        onClick={_handleToolbarButtonClick.bind(this, button)}
-        isActive={activeButtons.includes(button.id)}
-      />
-    );
+
+    if (hasNestedButtonDefinitions) {
+      return _getExpandableButtonComponent.call(_this, button, activeButtons);
+    }
+
+    return _getDefaultButtonComponent.call(_this, button, activeButtons);
   });
 }