Improved panel management - prevent resizing panels larger than available space

[peterflynn]

Fixes another part #2015 by maintaining panel max resize limits based on currently available slack space (i.e. space used by the editor area). This fixes part 1 of the 4-part list of issues there -- when dragging a panel to fill the whole UI, you can't overshoot and send the status bar (or other panels) sliding off the bottom of the window. And it gives us a clean foundation to build the remaining fixes on.

This also enables a cleaner fix to #3371 -- see pull #3931 which is based on this branch.

Here's what's changed:

• PanelManager provides APIs to create panels below the editor area. JSLint
  and Find in Files now use these APIs. (Find in Files panel UI is now moved out of main-view.html into a template).
• Move editor-holder ht calculations from EditorManager to PanelManager
• EditorManager listens to PanelManager for resize notifications. PanelManager
  listens for window resize (moved from EditorManager) and for Resizer events
  on all bottom panels. The old EditorManager.resizeEditor() API is still used
  for edge cases such as status & search bar show/hide, extensions that add
  fixed top panels, and extensions that don't use Resizer APIs to hide/show
  panels.
• Since PanelManager is listening, Resizer no longer pings EditorManager
  directly about show/hide/resize. (This would let us use Resizer as a generic splitter widget in other parts of the UI if needed).
• Resizer emits events to notify PanelManager about any panels it may have missed (legacy extensions that add panels via
  Resizer instead of PanelManager).
• Add max-size support to Resizer. Change Resizer min/max limits to operate in terms of panel outer height.
• PanelManager updates all bottom panels' max sizes when anything is resized/shown/hidden.

[peterflynn]

One thing I was on the fence about: it might be cleaner to move this line into PanelManager.triggerEditorResize(). That way PanelManager owns the editor-holder height entirely, so that when "editorAreaResize" is fired the editor area has indeed already been resized. And then EditorManager is just listening for that to refresh editors, nothing more...

[gruehle]

Moving this into PanelManager.triggerEditorResize() sounds like a good idea. Did you try it? If everything seems to work, I'm inclined to take that change. If things don't work, there should be a FUTURE comment added to move it (and make it work :-) )

[gruehle]

Reviewing

[peterflynn]

Notes on backwards compatibility:

• If you create a bottom panel the old way, injecting into DOM yourself, then calling Resizer.makeResizable() -- you'll get a deprecation warning but PanelManager will still "discover" the panel.
• If you show/hide panels using the Resizer APIs -- everything continues to work. It's fully supported to use either the Resizer APIs or the methods on the new Panel object that PanelManager returns.
• If you show/hide bottom panels using raw $.show()/.hide() + a call to EditorManager.resizeEditor() -- all current functionality (including the new "editorAreaResize" event and the Bottom panels get messed up if they are resized to the maximum height #2015 partial fix) will still work. However, you probably won't get the benefit of future panel-related fixes, like Scroll to cursor if hidden by JSLint panel #3371 or the rest of Bottom panels get messed up if they are resized to the maximum height #2015.
• If you show/hide non-Resizer content in the editor area (e.g. the top panels added by RWDY and SVG Preview) by injecting into the DOM yourself & then calling EditorManager.resizeEditor() -- it will continue to work (and the new "editorAreaResize" event is still fired).

I tested a number of extensions to verify this:

• brackets-sidebar-plus -- uses raw jQuery without calling resizeEditor(), but since this is a side panel it causes a bug only in the edge case of HTML menubar wrap (and that was true before this pull request too). (Filed When HTML menubar enabled, rendering issue at bottom of editor in some edge cases sathyamoorthi/brackets-sidebar-plus#4 to track that).
• brackets-tab extension -- uses Resizer.toggle(), works fine.
• brackets-jshint -- uses makeResizable() to create bottom panel, uses raw jQuery + resizeEditor() to show/hide. Gets a deprecation warning but works fine.
• PGB -- similar, also works fine
• brackets-display-shortcuts -- similar, also works fine

[gruehle]

The JSDoc for createBottomPanel() says the id param should be in package format. Should this be "search.results"?

[peterflynn]

Will fix. I'll add a brackets. prefix too, to avoid collisions in case extension authors ignore the advice and use generic, short names.

[gruehle]

Initial review complete.

[gruehle]

Looks good! Merging.