add interface documentation (partial)

papers/doc/2-interface/README.md

@@ -1,3 +1,6 @@
 # interface
 
-TODO
+the Furnace user interface is where the job gets done.
+
+- [UI components](components.md)
+- [global keyboard shortcuts](keyboard.md)

papers/doc/2-interface/components.md

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+# UI components
+
+the user interface consists of several components. this paper describes some of them.
+
+## windows
+
+TODO: image
+
+windows may be moved, collapsed, closed or even docked around the workspace.
+
+to move a window, press and hold the mouse button while on title bar or any empty space on it.
+then drag your mouse, and release it to stop moving.
+
+to resize a window, drag any of the bottom corners (marked by triangular tabs).
+
+to collapse a window, click on the triangle in the title bar.
+clicking again expands it.
+
+to close a window, click on the `X` at the top right corner.
+
+### arrangement and docking
+
+windows may be docked, which comes in handy.
+
+to dock a window, drag it from its title bar to another location in the workspace or to the location of another window.
+
+while dragging, an overlay with five options will appear, allowing you to select where and how to dock that window.
+the options are:
+
+```
+        UP
+ LEFT CENTER RIGHT
+       DOWN
+```
+
+drag your mouse cursor to any of the options to dock the window.
+
+if you drag the window to `CENTER`, the window will be maximized to cover the workspace (if you do this on the workspace), or it will appear as another tab (if you do this on a window).
+
+otherwise the window will be split in two, with the first half covered by the window you docked and the second half covered by the other window.
+
+when a window is docked, its title bar turns into a tab bar, and the function provided by the "collapse" triangle at the top left changes.
+
+if this triangle is clicked, a menu will appear with a single option: "Hide tab bar".
+selecting this option will hide the tab bar of that window.
+to bring it back, click on the top left corner.
+
+to undock a window, drag its tab away from where it is docked. then it will be floating again.
+
+## text fields
+
+TODO: image
+
+text fields are able to hold... text.
+
+click on a text field to start editing, and click away to stop editing.
+
+the following keyboard shortcuts work while on a text field:
+
+- `Ctrl-X`: cut
+- `Ctrl-C`: copy
+- `Ctrl-V`: paste
+- `Ctrl-Z`: undo
+- `Ctrl-Y`: redo
+- `Ctrl-A`: select all
+
+(replace Ctrl with Command on macOS)
+
+## number input fields
+
+TODO: image
+
+these work similar to text fields, but you may only input numbers.
+
+they also usually have two buttons which allow you to increase/decrease the amount when clicked (and rapidly do so when click-holding).
+
+## sliders
+
+TODO: image
+
+sliders are used for controlling values in a quick manner by being dragged.
+
+alternatively, Ctrl-clicking a slider (Command-click on macOS) will turn it into a number input field for a short period of time, allowing you to input fine values.

papers/doc/2-interface/keyboard.md

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+# global keyboard shortcuts
+
+this is a list of available shortcuts that may be used at any time, regardless of currently focused window.
+
+key        | action
+-----------|-----------------------
+Ctrl-O     | open file
+Ctrl-S     | save file
+Enter      | play/stop song
+F5/F6      |  "
+Shift-Enter| play from cursor position
+F7         |  "
+Ctrl-Enter | play one row
+NumPad `/` | decrease octave
+NumPad `*` | increase octave