Split Views and Toolbars

Written by Sergey I. Yevtushenko

[Note: here is a link to the cell_src.zip source code for this article. Ed.]

Foreword
This article will try to explain techniques which can be used to build PM applications with more-or-less modern user interfaces.

The term "modern user interface" means just some "bells and whistles" which will make your program at least as usable and user friendly as the best programs on the market.

These "bells and whistles" can be divided into two relatively independent parts. First is split views. This is a representation of information in windows split (horizontally or vertically or both) into two or more parts. You can find this style in many commercial and shareware programs. For example look at PMMail or the mail and news clients in Netscape Navigator. The main thing in split views is the possibility for users to change the sizes of parts of the split views as they like. So, for example, a window split into two parts will really consist of three parts: two panels and the splitbar itself. The second part is toolbars. This theme is common in EDM/2 issues, but the main goal of previous articles in EDM/2 was to build toolbars with minimal effort for the developer, but not to build toolbars which really can improve usability and/or the look of application.

These pieces were implemented in the usual way: I just subclass window procedures for many standard windows. To make the developer's life easy, the details of this were hidden behind a simple high level interface. I considered using the C language for implementation just because something written in C can be easily be used in C++ programs, but the reverse is not true. The second reason was even simpler: size and speed. With this package you can write very small applications, where the ratio of functionality code vs. interface code is near 1.

Using Package
As I mentioned, the use of the package is very simple: you create some structures filled with constants, call one function and get a window created for you. Take a look at example code (simple.c): CellDef cdLeftPane = {    CELL_WINDOW, WC_LISTBOX, "List", LS_NOADJUSTPOS | WS_VISIBLE, ID_LPANE }; This declaration defines one panel for a split view which will consist of just a simple listbox. This listbox will have window ID ID_LPANE. Another declaration: CellDef cdRightPane = {    CELL_WINDOW, WC_MLE, "SampleText", MLS_BORDER | WS_VISIBLE, ID_RPANE }; This is also a simple MLE with window ID set to ID_RPANE, with border (MLS_BORDER is set) and with text "Sample Text" in it. The third declaration is more complicated: CellDef mainClient = {    CELL_VSPLIT | CELL_SPLITBAR | CELL_SPLIT30x70, 0,    "Simple", FCF_TITLEBAR | FCF_SYSMENU | FCF_MENU | FCF_MINMAX  | FCF_TASKLIST | FCF_SIZEBORDER | 0,    MAIN_FRAME, &cdLeftPane, &cdRightPane, 0,    MainClientProc }; This declaration will define the main application window. You can note the difference in flags. Instead of CELL_WINDOW, we create a vertically split window (CELL_VSPLIT), which will have a splitbar (CELL_SPLITBAR), initially divided into 30/70% of the window width for left and right parts of the window, respectively. Window classes (second argument) have no meaning for this case, they are always WC_FRAME. Also, instead of window creation flags (fourth argument), there are frame creation flags. More detailed explanations of meanings of these flags can be found in the toolkit documentation. This window will have ID MAIN_FRAME, two panels (description for which is in cdLeftPane and cdRightPane respectively), and have client window procedure "MainClientProc". In doing this procedure, we subclass the procedure for the internal window class CELL_CLIENT. So, you need to call the subclassed procedure at the end of message processing. For this purpose you receive a pointer to structure WindowCellCtlData (defined in cell.h) by issuing a call to WinQueryWindowULong. For now this structure contains only one field, but you can add any necessary fields. Because this structure will be allocated for you in the package code and they need to know the size of it, you should recompile cell.c each time you make changes in WindowCellCtlData. The rest of the fields will be filled with 0 with the same code.

Now we ready to create the main window for the application. This is done by calling CreateCell. This function takes three parameters: definition of the window (explained above), a window handle for the parent window and a window handle for the owner window. The last parameter for the main window should be 0. In all other cases, this parameter should be set to windows which will receive notification messages from other windows. Usually this is the main window of the application. You should note that the main application window definition does not have the flag WS_VISIBLE set. This is important, because after creating windows, we may need to do some other work before the application window will appear on the screen.

What else do we need to do? We need fill controls with some data, add the toolbar and set the main window position on the screen.

Creating the toolbar is similar to creating windows: you fill structures, call a function and get a toolbar in your application. The structure contains three elements: flags, toolbar ID and a pointer to an array of button ID's. Note that the last element in this array is 0. This signals the end of the toolbar button definitions. For all IDs listed in the button array, you should define bitmaps in the resource file and optionally an element in the stringtable. The element in the string table is needed only if in the toolbar flags you set the flag TB_BUBBLE. If you want to divide buttons into groups with gaps between them, you can use the predefined flag ID TB_SEPARATOR. For this ID you do not need to define bitmaps or stringtable elements (indeed, separators are not even buttons). The function CreateToolbar receives two parameters: a pointer to the toolbar definition structure and the handle of the parent window. Really, this is just a window with which the toolbar will communicate when attaching/detaching, and which will own (and receive messages from) the buttons contained in the toolbar. A few words about toolbar flags: they define the look of the toolbar only at the starting of the application and can be changed by user. The flags TB_ATTACHED_* define the side of the parent window to which the toolbar will be attached initially: TB_ATTACHED_LT - left TB_ATTACHED_TP - top TB_ATTACHED_RT - right TB_ATTACHED_BT - bottom If none of these are specified, the toolbar will float detached from the parent window. Setting the flag TB_VERTICAL together with one of the TB flags will be ignored. The user can at any time change the toolbar state. Toolbar have a "hand" for dragging, so the user can drag the attached toolbar and detach it from the window. By double-clicking with the left mouse button on this "hand" button, the user can change the orientation of the detached toolbar (horizontal/vertical). By double-clicking with the right mouse button on the "hand" you will disable/enable bubble help, if this was allowed by the developer (by setting the TB_BUBBLE flag). To fill controls with data you need to know the window handle of the control. This not a problem if you created this control, but this is not the case. For this purpose you can use the function CellWindowFromID.

As you can see, this package is powerful enough to build applications with a modern user-friendly interface. Although this has not been explained before, your application is not restricted to having windows split into only two parts. Each panel can also be a split view. This can be achieved by specifying the proper flags in the subwindow definition structure. Another thing not explained is the possibility of having panels with fixed width. This can be done by toggling the flag CELL_FIXED. Furthermore, you can have panels with fixed absolute size and with fixed relative size. If you not specify the flag CELL_SPLITBAR, you will get windows with panels whose sizes will change with the main window's size, but the relationship between them remains intact. I should note that you can't have both panels with fixed absolute size, but this was not the goal :).

Final Words
This package was developed for my own purpose and you should always keep in mind that package may not exactly respond to your needs. But you have the sources, so do what you need to yourself :) You can use this code as you wish, as long as you don't forget to send me e-mail about this fact. Also, I would be pleased to know about any bugs which you find in my code.