Timeline: add the typical framework for custom drawing on the canvas

see gtk-canvas-experiment.cpp

src/stage/timeline/body-canvas-widget.cpp

@@ -77,12 +77,12 @@ namespace timeline {
       this->property_expand() = true;                               //  dynamically grab any available additional space
       this->add(canvas_);
       
-      { // for the initial empty canvas -- use space the enclosing scrolled window got.
+      { // for the initial empty canvas -- use all space the enclosing scrolled window got.
         auto currSize = get_allocation();
         canvas_.set_size (currSize.get_width(), currSize.get_height());
       }
       
-      // show everything....
+      // realise all initially configured elements....
       this->show_all();
     }
   
@@ -101,7 +101,103 @@ namespace timeline {
   {
     canvas_.rootBody_ = &rootTrackBody;
   }
-
+  
+  
+  /**
+   * Custom drawing of the timeline content area.
+   * The inherited `Gtk::Layout::on_raw(Context)` handles all drawing of child widgets placed onto the virtual canvas.
+   * Thus we need to fill in the structure of the tracks in the timeline background, and any non-standard overlay elements,
+   * including tags and markers, indicators, locators (edit point and playhead) and (semi-transparent) range selections.
+   * @todo according to the documentation for `signal_draw()`, the framework passes the actually visible area as clipping
+   *       region. In theory, this information could be used to reduce the load of canvas painting and repainting, which
+   *       becomes crucial for responsiveness on large sessions          ////////////////////////////////////TICKET #1191   
+   */
+  bool
+  TimelineCanvas::on_draw (Cairo::RefPtr<Cairo::Context> const& cox)
+  {
+    // draw track structure behind all widgets
+    openCanvas (cox);
+    drawGrounding (cox);
+    closeCanvas (cox);
+    
+    // cause child widgets to be redrawn
+    bool event_is_handled = Gtk::Layout::on_draw(cox);
+    
+    // draw dynamic markers and locators on top
+    openCanvas (cox);
+    drawOverlays (cox);
+    closeCanvas (cox);
+    
+    return event_is_handled;
+  }
+  
+  
+  /**
+   * Prepare the drawing canvas to work within our virtual canvas coordinate system.
+   * @remarks GTK passes a context related to the actual window area; however, we need to create
+   *   a uniform virtual canvas, shared by the child widgets, the backgrounding and any overlays.
+   *   To make this work, we have to connect to the scrollbar adjustments, since GTK does this
+   *   only for the child widgets on the canvas, not for any custom painting.
+   */
+  void
+  TimelineCanvas::openCanvas (Cairo::RefPtr<Cairo::Context> const& cox)
+  {
+    auto adjH = get_hadjustment();
+    auto adjV = get_vadjustment();
+    double offH = adjH->get_value();
+    double offV = adjV->get_value();
+    
+    cox->save();
+    cox->translate(-offH, -offV);
+  }
+  
+  
+  /**
+   * Finish and close the virtual drawing canvas established by #openCanvas().
+   * Discard any coordinate offsets, stroke and drawing settings applied within. 
+   */
+  void
+  TimelineCanvas::closeCanvas (Cairo::RefPtr<Cairo::Context> const& cox)
+  {
+    cox->restore();
+  }
+  
+  
+  /**
+   * Establish and render the structure of (possibly nested) tracks and overview rulers.
+   * @param cox cairo drawing context for custom drawing, adjusted for our virtual canvas.
+   */
+  void
+  TimelineCanvas::drawGrounding (Cairo::RefPtr<Cairo::Context> const& cox)
+  {
+    /////////////////////////////////////////////TICKET #1139 : placeholder drawing
+    cox->set_source_rgb(0.8, 0.0, 0.0);
+    cox->set_line_width (5.0);
+    cox->rectangle(0,0, 80, 40);
+    cox->stroke();
+    /////////////////////////////////////////////TICKET #1139 : placeholder drawing 
+  }
+  
+  
+  /**
+   * 
+   * @param cox cairo drawing context of the virtual canvas for custom drawing.
+   */
+  void
+  TimelineCanvas::drawOverlays (Cairo::RefPtr<Cairo::Context> const& cox)
+  {
+    /////////////////////////////////////////////TICKET #1139 : placeholder drawing
+    auto alloc = get_allocation();
+    int w = alloc.get_width();
+    int h = alloc.get_height();
+    int rad = MIN (w,h) / 2;
+    
+    cox->set_source_rgb(0.2, 0.4, 0.9);     // blue
+    cox->set_line_width (2.0);
+    cox->arc(rad, rad, rad, 0.0, 2.0*M_PI); // full circle
+    cox->stroke();
+    /////////////////////////////////////////////TICKET #1139 : placeholder drawing 
+  }
   
   
   

src/stage/timeline/body-canvas-widget.hpp

@@ -31,13 +31,13 @@
  ** on top of Gtk::Layout, allows to combine _custom drawing_ with the placement of
  ** embedded child widgets, where the latter's layout is again managed automatically
  ** by the toolkit set. This approach allows us to circumvent some of the perils of
- ** custom drawing, where we might forfeit several of the benefits of using a toolkit
+ ** custom drawing, where we might forfeit several of the benefits of using a toolkit,
- ** unintentionally, and create an UI which feels foreign and brittle in comparison
+ ** unintentionally of course, and create an UI which feels foreign and brittle
- ** to standard software.
+ ** in comparison to standard software.
  ** 
  ** # Layout management
  ** 
- ** To create a consistent layout of the timeline, header pane and body need to react
+ ** To create a consistent timeline layout, the header pane and body need to react
  ** to the same scrolling adjustments, and use the same vertical size allocations for
  ** each embedded track. Such a consistent global layout needs to be built up in a
  ** *display evaluation pass*, carried out collaboratively between the building blocks
@@ -45,8 +45,8 @@
  ** as (view) model entities, visited by the timeline::LayoutManager to establish
  ** coherent display parameters. From within this evaluation pass, the individual
  ** presenters communicate with their _slave widgets,_ which are inserted into the
- ** display context of the track header pane or this body widget respectively. As
+ ** display context of the track header pane or into this body widget respectively.
- ** a result, some new widgets may be injected, existing widgets may be removed or
+ ** As result, some new widgets may be injected, existing widgets might be removed or
  ** hidden, and other widgets may be relocated to different virtual canvas coordinates.
  ** 
  ** @todo WIP-WIP-WIP as of 12/2016
@@ -79,6 +79,15 @@ namespace timeline {
       TrackBody* rootBody_;
       
       TimelineCanvas();
+      
+    private:
+      virtual bool on_draw (Cairo::RefPtr<Cairo::Context> const&)  override;
+      
+      void openCanvas (Cairo::RefPtr<Cairo::Context> const&);
+      void closeCanvas (Cairo::RefPtr<Cairo::Context> const&);
+      
+      void drawGrounding (Cairo::RefPtr<Cairo::Context> const&);
+      void drawOverlays (Cairo::RefPtr<Cairo::Context> const&);
     };
   
   

src/stage/timeline/timeline-layout.hpp

@@ -51,8 +51,8 @@
  ** Thus we strive to break up the whole process of controlling the layout into several
  ** local concerns, each of which can be made self contained. The backbone is formed by
  ** a recursive collaboration between two abstractions (interfaces)
- ** - the building blocks of the timeline expose the interface timeline::Element
+ ** - the building blocks of the timeline expose the interface timeline::Element (TODO 12/18 really?)
- ** - the global timeline widget implements a timeline::LayoutManager interface
+ ** - the global timeline widget implements a timeline::LayoutManager interface (TODO 12/18 work out the crucial point of that interface!)
  ** 
  ** ## Display evaluation pass
  ** 

src/stage/timeline/track-body.cpp

@@ -66,7 +66,7 @@ namespace timeline {
   
   TrackBody::TrackBody()
     : overviewHeight_{DEFAULT_OVERVIEW_HEIGHT_px}
-    , contentHeight_{DEFAULT_OVERVIEW_HEIGHT_px}
+    , contentHeight_{DEFAULT_CONTENT_HEIGHT_px}
     , subTracks_{}
     { }
   

src/stage/timeline/track-body.hpp

@@ -64,7 +64,7 @@ namespace timeline {
    * A given TrackBody works with coordinates relative to its vertical starting point;
    * coordinates on the TimelineCanvas operate from top downwards. The fundamental
    * task of a TrackBody is to find out about its own overall height, including the
-   * overall height require by all its nesting children. Moreover, the height of
+   * overall height required by all its nested children. Moreover, the height of
    * the content area needs to be negotiated with the actual content elements.
    * @todo WIP-WIP as of 10/2018
    */

wiki/thinkPad.ichthyo.mm

@@ -19423,8 +19423,7 @@
       ...in dem der Timeline body-canvas nämlich liegt
     </p>
   </body>
-</html>
+</html></richcontent>
-</richcontent>
 <icon BUILTIN="idea"/>
 </node>
 </node>
@@ -19577,7 +19576,7 @@
 <icon BUILTIN="flag-yellow"/>
 <node BACKGROUND_COLOR="#fdfdcf" COLOR="#ff0000" CREATED="1540640109628" ID="ID_147809215" MODIFIED="1540640128945" TEXT="TODO: TimelineGui (proxy) mu&#xdf; kaskadieren">
 <icon BUILTIN="flag-pink"/>
-<node BACKGROUND_COLOR="#fdfdcf" COLOR="#ff0000" CREATED="1544135984042" ID="ID_429363053" MODIFIED="1544310842213" TEXT="Grund f&#xfc;r den Fehler im Nexus?">
+<node BACKGROUND_COLOR="#fdfdcf" COLOR="#ff0000" CREATED="1544135984042" ID="ID_429363053" MODIFIED="1544136004274" TEXT="Grund f&#xfc;r den Fehler im Nexus?">
 <richcontent TYPE="NOTE"><html>
   <head>
     
@@ -21297,7 +21296,7 @@
 <node CREATED="1541860174509" ID="ID_983216306" MODIFIED="1541860194622" TEXT="position within window">
 <node CREATED="1541860195426" ID="ID_1143510761" MODIFIED="1541860197638" TEXT="relative"/>
 <node CREATED="1541860198222" ID="ID_847832000" MODIFIED="1541860200197" TEXT="absolute">
-<node CREATED="1544126105472" ID="ID_1636490570" MODIFIED="1544310842664" TEXT="relative-absolute">
+<node CREATED="1544126105472" ID="ID_1636490570" MODIFIED="1544126149549" TEXT="relative-absolute">
 <richcontent TYPE="NOTE"><html>
   <head>
     
@@ -21319,7 +21318,7 @@
 </node>
 <node CREATED="1542384160498" ID="ID_1252241860" MODIFIED="1542384163677" TEXT="TimeWindow">
 <node CREATED="1542384165737" ID="ID_705415129" MODIFIED="1542384177115" TEXT="die konkret sichbare TimeSpan"/>
-<node CREATED="1542384188438" ID="ID_444895141" MODIFIED="1544310842677" TEXT="stets in realem relativem Zeitma&#xdf;">
+<node CREATED="1542384188438" ID="ID_444895141" MODIFIED="1542384280140" TEXT="stets in realem relativem Zeitma&#xdf;">
 <richcontent TYPE="NOTE"><html>
   <head>
     
@@ -21334,8 +21333,7 @@
       </li>
     </ul>
   </body>
-</html>
+</html></richcontent>
-</richcontent>
 </node>
 </node>
 <node CREATED="1541859633805" ID="ID_304890799" MODIFIED="1541859637628" TEXT="Scale">
@@ -21383,7 +21381,7 @@
 <node CREATED="1541860828603" ID="ID_111513506" MODIFIED="1541860839002" TEXT="Zeit"/>
 <node CREATED="1541860831875" ID="ID_1775831703" MODIFIED="1541860835311" TEXT="Extension"/>
 </node>
-<node CREATED="1541860818012" FOLDED="true" ID="ID_814200290" MODIFIED="1541860825864" TEXT="vertikale Dimension stets topologisch">
+<node CREATED="1541860818012" FOLDED="true" ID="ID_814200290" MODIFIED="1544127129504" TEXT="vertikale Dimension stets topologisch">
 <node CREATED="1544127119809" ID="ID_431805088" MODIFIED="1544127122858" TEXT="nicht immer...."/>
 <node CREATED="1544127123803" ID="ID_1360167609" MODIFIED="1544127127665" TEXT="Ausnahme: Kurven"/>
 </node>
@@ -40734,8 +40732,7 @@
       ...also <i>abz&#252;glich</i>&#160;Dekoration und Margin
     </p>
   </body>
-</html>
+</html></richcontent>
-</richcontent>
 </node>
 <node CREATED="1542308990570" ID="ID_1371068296" MODIFIED="1542309000371" TEXT="stets komplett in der zugewiesenen Allocation enthalten"/>
 </node>