[3SP, 3.5SP] UI: Toolbar supporting custom sub-menus

[ivan-cukic]

The toolbar should have buttons for

• sub-menu to choose selector (initially string entry only, ala. FAIR.SELECTOR.C=0:S=1:P=0, FAIR.SELECTOR.C=0:S=1:P=-1, or FAIR.SELECTOR.C=*
• controlling scheduler execution - start/stop

pre-requisite to be completed: fair-acc/gnuradio4#210

[Waqar144]

• The primary task to have a default toolbar in the UI that is shown/populated if there are 'drawable' blocks in the flow-graph
• A block will need have a drawable type, probably an enum e.g., enum { Toolbar, Chart, None }.
• Whenever there is a drawable Block detected the UI should keep a weak reference and invoke the Block::draw() method. See example here https://github.com/fair-acc/graph-prototype/pull/250/files
• The first two types of blocks would be

  1. play-stop (run once and then stop), play (run until stopped or paused), continuous (<-> streaming mode), pause and stop (initially deactivated) requires the corresponding state-machine should emit a Message containing the corresponding 'pushed'/'released'/'active state' info
     

  2. basic label that shows the last received control message received via MsgPortIn ctrl_in

  3. optional: combo box with both ctrl_[in,out] that received and shows a received message (add this to the existing list) or emit a message if the user changes the selected index

• to be discussed: design of lifecycle management of UI blocks (when to keep/destroy, etc.)
• this would be followed-up with the 'chart' type blocks: [3-5SP, 5SP] UI: Implement charts that can show DataSets #132

[Waqar144]

Current state of the toolbar UI

[Waqar144]

• There are 2 new block types representing Toolbar blocks now: GRPlayStopToolbarBlock and GRLabelToolbarBlock. The types are defined in toolbar_blocks.h and are registed in main.cpp.
• DigitizerUI::Block has a new draw() function which can be implemented to draw a Drawable block.
• DigitizerUI::Block has a new function isToolbarBlock() which returns true if the block is of ui::Category::Toolbar type