Question

I’ve been developing a gui for some time, which requires the creation of common control objects that Mathematica lacks (e.g. spinner, treeview, openerbar, etc.). One is the multipanel, i.e. a pane object that is split into two (or more) subpanes, where the divider can be set by the mouse. Here is my version of a dual pane. I would like to hear your opinion and ideas about how to expand it to handle not just 2 but any number of subpanes, and also how to optimize it. At present, for heavily loaded subpanes, it lags terribly, no idea why.

Options[SplitPane] = {Direction -> "Vertical", 
   DividerWidth -> Automatic, Paneled -> {True, True}};
SplitPane[opts___?OptionQ] := 
  Module[{dummy}, SplitPane[Dynamic[dummy], opts]];
SplitPane[val_, opts___?OptionQ] := SplitPane[val, {"", ""}, opts];
SplitPane[val_, content_, opts___?OptionQ] := 
  SplitPane[val, content, {100, 50}, opts];
SplitPane[Dynamic[split_, arg___], {expr1_, expr2_}, {maxX_, maxY_}, 
   opts___?OptionQ] := 
  DynamicModule[{temp, dir, d, panel, coord, max, fix, val},
   {dir, d, panel} = {Direction, DividerWidth, Paneled} /. {opts} /. 
     Options[SplitPane];
   dir = dir /. {Bottom | Top | "Vertical" -> "Vertical", _ -> 
       "Horizontal"};
   d = d /. Automatic -> 2;
   split = If[NumberQ[split], split, max/2];
   val = Clip[split /. {_?NumberQ -> split, _ -> maxX/2}, {0, maxX}];
   {coord, max, fix} = 
    Switch[dir, "Vertical", {First, maxX, maxY}, 
     "Horizontal", {(max - Last[#]) &, maxY, maxX}];
   panel = (# /. {None | False -> 
          Identity, _ -> (Panel[#, ImageMargins -> 0, 
             FrameMargins -> -1] &)}) & /@ panel;

   Grid[If[dir === "Vertical",
     {{
       Dynamic[
        panel[[1]]@
         Pane[expr1, ImageSize -> {split - d, fix}, 
          ImageSizeAction -> "Scrollable", Scrollbars -> Automatic, 
          AppearanceElements -> None], TrackedSymbols :> {split}],
       Deploy@EventHandler[
         MouseAppearance[
          Pane[Null, ImageSize -> {d*2, fix}, ImageMargins -> -1, 
           FrameMargins -> -1], "FrameLRResize"],
         "MouseDown" :> (temp = 
            coord@MousePosition@"CellContentsAbsolute"; 
           split = 
            If[Abs[temp - split] <= d \[And] 0 <= temp <= max, temp, 
             split]), 
         "MouseDragged" :> (temp = 
            coord@MousePosition@"CellContentsAbsolute"; 
           split = If[0 <= temp <= max, temp, split])],
       Dynamic@
        panel[[2]]@
         Pane[expr2, ImageSizeAction -> "Scrollable", 
          Scrollbars -> Automatic, AppearanceElements -> None, 
          ImageSize -> {max - split - d, fix}]
       }},
     {
      List@
       Dynamic[panel[[1]]@
         Pane[expr1, ImageSize -> {fix, split - d}, 
          ImageSizeAction -> "Scrollable", Scrollbars -> Automatic, 
          AppearanceElements -> None], TrackedSymbols :> {split}],
      List@Deploy@EventHandler[
         MouseAppearance[
          Pane[Null, ImageSize -> {fix, d*2}, ImageMargins -> -1, 
           FrameMargins -> -1], "FrameTBResize"],
         "MouseDown" :> (temp = 
            coord@MousePosition@"CellContentsAbsolute"; 
           split = 
            If[Abs[temp - split] <= d \[And] 0 <= temp <= max, temp, 
             split]), 
         "MouseDragged" :> (temp = 
            coord@MousePosition@"CellContentsAbsolute"; 
           split = If[0 <= temp <= max, temp, split])],
      List@
       Dynamic[panel[[2]]@
         Pane[expr2, ImageSizeAction -> "Scrollable", 
          Scrollbars -> Automatic, 
          ImageSize -> {fix, max - split - d}, 
          AppearanceElements -> None], TrackedSymbols :> {split}]
      }
     ], Spacings -> {0, -.1}]
   ];
SplitPane[val_, arg___] /; NumberQ[val] := 
  Module[{x = val}, SplitPane[Dynamic[x], arg]];

pos = 300;
SplitPane[
 Dynamic[pos], {Manipulate[
   Plot[Sin[x (1 + a x)], {x, 0, 6}], {a, 0, 2}], 
  Factorial[123]}, {500, 300}]

Answer 1

The key to generalizing to several panels was to refactor your code. In its present form, while very nice, it was mixing visualization / UI primitives and options with the split logic, and had lots of duplicate code. This made generalization hard. Here is the refactored version:

ClearAll[SplitPane];
Options[SplitPane] = {
    Direction -> "Vertical", DividerWidth -> Automatic, Paneled -> True
};
SplitPane[opts___?OptionQ] :=   Module[{dummy}, SplitPane[Dynamic[dummy], opts]];
SplitPane[val_, opts___?OptionQ] := SplitPane[val, {"", ""}, opts];
SplitPane[val_, content_, opts___?OptionQ] :=
    SplitPane[val, content, {100, 50}, opts];
SplitPane[sp_List, {cont__}, {maxX_, maxY_}, opts___?OptionQ] /; 
        Length[sp] == Length[Hold[cont]] - 1 :=
  Module[{scrollablePane, dividerPane, onMouseDownCode, onMouseDraggedCode, dynPane,
      gridArg, split, divider, panel},
    With[{paneled = Paneled /. {opts} /. Options[SplitPane],len = Length[Hold[cont]]},
       Which[
          TrueQ[paneled ],
             panel = Table[True, {len}],
          MatchQ[paneled, {Repeated[(True | False), {len}]}],
             panel = paneled,
          True,
            Message[SplitPane::badopt]; Return[$Failed, Module]
       ]
    ];

    DynamicModule[{temp, dir, d, coord, max, fix, val},
      {dir, d} = {Direction, DividerWidth}/.{opts}/.Options[SplitPane];
      dir =  dir /. {
         Bottom | Top | "Vertical" -> "Vertical", _ -> "Horizontal"
      };
      d = d /. Automatic -> 2;
      val = Clip[sp /. {_?NumberQ -> sp, _ -> maxX/2}, {0, maxX}];
      {coord, max, fix} =
        Switch[dir,
          "Vertical",
             {First, maxX, maxY},
          "Horizontal",
             {(max - Last[#]) &, maxY, maxX}
        ];
      Do[split[i] = sp[[i]], {i, 1, Length[sp]}];
      split[Length[sp] + 1] = max - Total[sp] - 2*d*Length[sp];
      panel =
          (# /. {
            None | False -> Identity, 
            _ -> (Panel[#, ImageMargins -> 0,FrameMargins -> -1] &)
           }) & /@ panel;
      scrollablePane[args___] :=
          Pane[args, ImageSizeAction -> "Scrollable", 
               Scrollbars -> Automatic, AppearanceElements -> None];
      dividerPane[size : {_, _}] :=
          Pane[Null, ImageSize -> size, ImageMargins -> -1,FrameMargins -> -1];

      onMouseDownCode[n_] := 
        Module[{old},
          temp = coord@MousePosition@"CellContentsAbsolute";
          If[Abs[temp - split[n]] <= d \[And] 0 <= temp <= max,
            old = split[n];
            split[n] = temp-Sum[split[i], {i, n - 1}];
            split[n + 1] += old - split[n];       
        ]];

      onMouseDraggedCode[n_] :=
         Module[{old},
            temp = coord@MousePosition@"CellContentsAbsolute";
            If[0 <= temp <= max,
               old = split[n];
               split[n] = temp -Sum[split[i], {i, n - 1}];
               split[n + 1] += old - split[n];
            ] ;
         ];

      SetAttributes[dynPane, HoldFirst];
      dynPane[expr_, n_, size_] :=
          panel[[n]]@scrollablePane[expr, ImageSize -> size];

      divider[n_, sizediv_, resizeType_] :=
         Deploy@EventHandler[
            MouseAppearance[dividerPane[sizediv], resizeType],
           "MouseDown" :> onMouseDownCode[n],
           "MouseDragged" :> onMouseDraggedCode[n]
         ];

      SetAttributes[gridArg, HoldAll];
      gridArg[{content__}, sizediv_, resizeType_, sizeF_] :=
         Module[{myHold, len = Length[Hold[content]] },
           SetAttributes[myHold, HoldAll];
           List @@ Map[
             Dynamic,
             Apply[Hold, 
                MapThread[Compose,
                   {
                      Range[len] /. {
                        len :>               
                          Function[
                             exp, 
                             myHold[dynPane[exp, len, sizeF[len]]], 
                             HoldAll
                          ],
                        n_Integer :>
                          Function[exp,
                             myHold[dynPane[exp, n, sizeF[n]],
                                divider[n, sizediv, resizeType]
                             ], 
                          HoldAll]
                      },
                      Unevaluated /@ Unevaluated[{content}]
                    }] (* MapThread *)
               ] /. myHold[x__] :> x
           ] (* Map *)
         ]; (* Module *)
      (* Output *)
      Grid[
        If[dir === "Vertical",
           List@ gridArg[{cont}, {d*2, fix},"FrameLRResize",{split[#] - d, fix} &],
           (* else *)
           List /@ gridArg[{cont}, {fix, d*2},"FrameTBResize", {fix, split[#] - d} &]
        ],
        Spacings -> {0, -.1}]]];

SplitPane[val_, arg___] /; NumberQ[val] := 
   Module[{x = val}, SplitPane[Dynamic[x], arg]];

Here is how it may look:

SplitPane[{300, 300}, 
 {
   Manipulate[Plot[Sin[x (1 + a x)], {x, 0, 6}], {a, 0, 2}], 
   Factorial[123], 
   CompleteGraph[5]
 }, {900, 300}]

Can’t comment of performance problems you mentioned. Also, when you start dragging with the mouse, the real cursor position is often quite off with respect to the divider position. This is both for your and my versions, perhaps some more precise scaling is needed.

Just want to emphasize once again – generalization became only possible after I did the refactoring, to separate the splitting logic from the visualization-related things. As to the optimization, I also think that it will be much easier to attempt optimizing this version than the original one, for the same reasons.

EDIT

I hesitated a bit to add this note, but it must be mentioned that my solution above, while working, shows one practice which is considered bad by expert UI mma programmers. Namely, it uses Module– generated variables inside Dynamic inner to that Module (in particular, split in the code above, also various auxiliary functions). The reasons I used it are that I wasn’t able to make this work with only DynamicModule– generated variables, plus Module– generated variables always worked for me before. However, please see the post by John Fultz in this MathGroup thread, where he states that this practice should be avoided.