1*946379e7SchristosBefore you read the hello.cs source code: 2*946379e7Schristos 3*946379e7SchristosPreface about GUI Programming Methodologies 4*946379e7Schristos=========================================== 5*946379e7Schristos 6*946379e7SchristosThe traditional GUI programming methodology for Windows GUI programmers 7*946379e7Schristosis to assemble controls using a GUI builder. These GUI builders 8*946379e7Schristosdon't have good techniques for determining the size and position of the 9*946379e7Schristoscontrols depending on their contents. Instead, they *hardcode* the 10*946379e7Schristossize and positions of the controls in each panel, as fixed numbers, 11*946379e7Schristosmeasured in pixels. 12*946379e7Schristos 13*946379e7SchristosWhat are the consequences? 14*946379e7Schristos 15*946379e7Schristos1) Consequences for all users: 16*946379e7Schristos Such panels would not look nice when the user resizes them. So the 17*946379e7Schristos programmer simply makes the dialogs non-resizable. When such a 18*946379e7Schristos panel then contains a scrollable list of items, with 100 items and 19*946379e7Schristos a scroll window of 5 items, a user's normal reaction is to enlarge 20*946379e7Schristos the dialog, to see more items. But the dialog is not resizable! 21*946379e7Schristos Frustration. 22*946379e7Schristos 23*946379e7Schristos2) Consequences for disabled users: 24*946379e7Schristos Some users need bigger fonts for working comfortably. Guess what 25*946379e7Schristos happens when the user changes the size of the default system font? 26*946379e7Schristos Many labels in dialogs are truncated. 27*946379e7Schristos 28*946379e7Schristos3) Consequences for internationalization: 29*946379e7Schristos The translation of a term or label in another language often needs 30*946379e7Schristos more screen space. For example, Japanese translations often are 30% 31*946379e7Schristos longer than the original English label. Therefore, if only the strings 32*946379e7Schristos of a dialog are localized, many labels are truncated. 33*946379e7Schristos 34*946379e7SchristosProblems 1 and 2 are usually accepted in the Windows programmers 35*946379e7Schristoscommunity. (Problem 1 is not fatal, only frustrating. And problem 2 36*946379e7Schristosaffects only a small proportion of the users; they are simply ignored.) 37*946379e7SchristosProblem 3 is "solved" by letting the localization team not only translate 38*946379e7Schristosthe strings, but also redo the layout of each dialog. 39*946379e7Schristos 40*946379e7SchristosIn contrast, the methodology of programmers of the Qt/KDE, Gtk/GNOME, 41*946379e7SchristoswxWidgets, AWT, Swing, Tk toolkits is to have the positions and sizes 42*946379e7Schristosof controls determined at runtime, according to 43*946379e7Schristos - the needs of the control itself, 44*946379e7Schristos - the needs of the other controls in the panel, 45*946379e7Schristos - the available panel size, given by the user through resizing. 46*946379e7SchristosThe common technology for this approach is to group related controls 47*946379e7Schristostogether in containers, and perform size and position propagations 48*946379e7Schristosbetween the controls of the container, the container, the container's 49*946379e7Schristoscontainer etc. These computations are performed by so-called 50*946379e7Schristos"layout manager" objects. 51*946379e7SchristosOther technologies such as global constraint systems (as in Garnet) or 52*946379e7Schristosspring-like attachments are not so much in use anymore nowadays. 53*946379e7Schristos 54*946379e7SchristosThis programmed-resizing methodology solves the problems 1), 2) and 3). 55*946379e7Schristos 56*946379e7SchristosWhat are the associated costs and efforts? Taking the programmed-resizing 57*946379e7Schristosmethodology as baseline, the hardcoded sizes and positions approach has 58*946379e7Schristos - the advantage that the programmer saves about 1/3 of the GUI 59*946379e7Schristos programming work (namely choosing the layout managers and setting 60*946379e7Schristos alignment hints), 61*946379e7Schristos - the drawback that each localization team has much more work, namely 62*946379e7Schristos to rearrange the controls in the panel. 63*946379e7SchristosIn most free software projects, there are at least ca. 5 localizations; 64*946379e7Schristossuccessful projects even have 30 or 50 localizations. 65*946379e7SchristosIn other words, a program built with hardcoded sizes and positions 66*946379e7Schristoscannot afford many localizations, or the effort for localization will 67*946379e7Schristosbe prohibitively high. 68*946379e7Schristos 69*946379e7SchristosFor this reason, we strongly recommend to use the programmed-resizing 70*946379e7Schristosmethodology. In this example, since the Windows.Forms package lacks 71*946379e7Schristoslayout manager classes, we compute the layout by hand, through an 72*946379e7Schristosoverride of the OnResize method. For larger programs, we would recommend 73*946379e7Schristosto build a few simple layout managers, to get on par with the layout 74*946379e7Schristosabilities found in Qt, Swing, etc. 75*946379e7Schristos(The layout system of Gtk/GNOME is somewhat particular: It does not 76*946379e7Schristosprovide the ability to set a preferred alignment on controls like labels. 77*946379e7SchristosInstead one uses intermediate containers for the purpose of alignment.) 78*946379e7Schristos 79*946379e7SchristosAcknowledgement: This preface borrows ideas from an article of Luke Plant. 80*946379e7Schristos 81*946379e7SchristosCopyright (C) 2006 Free Software Foundation, Inc. 82