| author | William Roberts <williamr@symbian.org> |
| Wed, 07 Jul 2010 22:30:23 +0100 | |
| branch | GCC_SURGE |
| changeset 88 | 3c15ef939dd3 |
| parent 1 | 2fb8b9db1c86 |
| permissions | -rw-r--r-- |
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2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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<HTML><HEAD><TITLE>Using FrameWork and TextEdit</TITLE></HEAD> |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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<BODY> |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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<H1>Using FrameWork and TextEdit</H1> |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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<HR> |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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In this document we use the <CODE>FrameWork</CODE> and <CODE>TextEdit</CODE> |
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modules to create a simple text editor. The functionality |
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of the editor is very basic: you can open multiple files, type text and use |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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cut/copy/paste. The main intention is to explain the use of FrameWork, really. <p> |
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<H2>FrameWork</H2> |
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The FrameWork module provides you with a skeleton application. It declares a |
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number of classes suitable for subclassing in your application, thereby |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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releaving you of the burden of doing all event handling, etc. yourself. For a |
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real understanding you will have to browse the source. Here is a short overview |
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of the classes and what functionality they provide. |
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<dl> |
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<dt> <CODE>Application</CODE> |
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<dd> |
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This is the toplevel class you will override. It maintains the menu bar and contains |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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the main event handling code. Normal use is to override the <code>__init__</code> routine |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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to do your own initializations and override <code>makeusermenus</code> to create your menus |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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(your menu callback routines may be here too, but this is by no means necessary). |
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The event handling code can be overridden at various levels, from very low-level (the |
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<code>dispatch</code> method) to intermedeate level (<code>do_keyDown</code>, for instance) |
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to high-level (<code>do_key</code>). The application class knows about the <code>Window</code> |
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objects you create, and will forward events to the appropriate window (So, normally you |
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would have a <code>do_key</code> method in your window object, not your application object). |
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<dt> <CODE>MenuBar</CODE>, <CODE>Menu</CODE> and <CODE>MenuItem</CODE> |
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<dd> |
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These classes (and a few friends like <CODE>SubMenu</CODE>) handle your menus. You would not |
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normally override them but use them as-is. The idiom for creating menus is a bit strange, |
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see the test code at the bottom of FrameWork for sample use. The apple menu is handled for you |
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by <CODE>MenuBar</CODE> and <CODE>Application</CODE>. |
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<dt> <CODE>Window</CODE> |
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<dd> |
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The basic window. Again, a class that you normally subclass in your application, possibly |
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multiple times if you have different types of windows. The init call instantiates the data |
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structure but actually opening the window is delayed until you call <code>open</code>. Your |
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open method should call <code>do_postopen</code> to let the base class handle linking in to |
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the application object. Similarly with <code>close</code> and <code>do_postclose</code>. The |
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rest of the code is mainly event-oriented: you override <code>do_postresize</code>, |
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<code>do_contentclick</code>, <code>do_update</code>, <code>do_activate</code> |
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and <code>do_key</code> to "do your thing". When these methods are called the relevant environment |
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has been setup (like <code>BeginDrawing</code> has been called for updates, etc). |
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<dt> <CODE>windowbounds</CODE> |
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<dd> |
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Not a class but a function: you pass it a width and height and it will return you a rectangle |
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you can use to create your window. It will take care of staggering windows and it will try |
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to fit the window on the screen (but the resulting rect will <em>always</em> have the size you |
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specify). |
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<dt> <CODE>ControlsWindow</CODE> |
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<dd> |
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A subclass of Window which automatically handles drawing and clicking for controls. You override |
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the same methods as for Window (if you need to: control-related things are done automatically) and |
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<code>do_controlhit</code>. |
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<dt> <CODE>ScrolledWindow</CODE> |
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<dd> |
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A subclass of ControlsWindow, a window with optional scrollbars. If you override <code>do_activate</code> |
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or <code>do_postresize</code> you must call the ScrolledWindow methods at the end of your override. |
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You call <code>scrollbars</code> to enable/disable scrollbars and <code>updatescrollbars</code> to |
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update them. You provide <code>getscrollbarvalues</code> to return the current x/y values (a helper |
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method <code>scalebarvalues</code> is available) and <code>scrollbarcallback</code> to update your |
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display after the user has used the scrollbars. |
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<dt> <CODE>DialogWindow</CODE> |
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<dd> |
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A modeless dialog window initialized from a DLOG resource. See the |
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<A HREF="example2.html">second Interslip example</A> for its useage. |
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</dl> |
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<H2>A sample text editor</H2> |
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Let us have a look at <A HREF="textedit/ped.py">ped.py</A> (in the Demo:textedit folder), the Pathetic |
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EDitor. It has multiple windows, cut/copy/paste and keyboard input, but that is about all. It looks |
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as if you can resize the window but it does not work. Still, it serves as an example. |
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Ped creates two classes, <code>TEWindow</code> and <code>Ped</code>. Let us start with the latter one, |
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which is a subclass of <code>FrameWork.Application</code> and our main application. The init function |
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has little to do aside from the standard init: it remembers a window sequence number (for untitled windows), |
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and sets things up for menu disable to work. Remember, the <code>makeusermenus</code> is called |
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automatically. <p> |
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<code>Makeusermenus</code> creates the <code>File</code> and <code>Edit</code> menus. It also initializes |
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a couple of lists that are used later to correctly enable and disable menu items (and complete menus) depending |
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on whether a window is open, text is selected, etc. The callback functions for the menu items are |
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all methods of this class. <p> |
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96 |
<code>Updatemenubar</code> handles greying out (and re-enabling) of menu items depending on whether there |
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97 |
is a current window and its state. <p> |
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98 |
|
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99 |
The rest of the methods are all callbacks and simple to understand. They check whether there is an active |
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100 |
window (and complain loudly if there is none: the corresponding menu entry should have been disabled |
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101 |
in that case!) and call the appropriate window method. Only the <code>_open</code> method (the common code |
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102 |
for <code>Open</code> and <code>New</code>) deserves some mention. It instantiates a <code>TEWindow</code> |
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103 |
object and opens it with the title, filename and contents of the file to edit. Note that FrameWork takes |
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104 |
care of remembering the window object. A minor note on opening the file in binary mode: this is because |
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105 |
TextEdit expects MacOS style carriage-return terminated lines, not python/unix/C style newline-terminated |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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106 |
lines. <p> |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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107 |
|
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108 |
Oh yes: the <code>quit</code> callback does a little magic too. It closes all windows, and only if this |
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109 |
succeeds it actually quits. This gives the user a chance to cancel the operation if some files are unsaved. |
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110 |
<p> |
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111 |
|
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112 |
Lastly, there is the <code>idle</code> method, called by the Application base class when no event |
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113 |
is available. It is forwarded to the active window, so it can blink the text caret. <p> |
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114 |
|
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115 |
The <code>TEWindow</code> object handles a single window. Due to this structuring it is absolutely no |
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116 |
problem to have multiple windows open at the same time (although a real application should exercise care when |
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117 |
two windows refer to the same document). TEWindow uses the standard init code inherited from |
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118 |
<code>ScrolledWindow</code>, and sets itself up at the time of the <code>open</code> call. It obtains screen |
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119 |
coordinates, opens the window, creates rectangles for TextEdit to work in (the magical number <code>15</code> |
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here is the size of a normal scroll bar: unfortunately there is no symbolic constant for it), |
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121 |
creates the TextEdit object and initializes it with our data. Finally, the scroll bars are created (the |
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122 |
initial values will be obtained automatically through <code>getscrollbarvalues</code>) and we activate |
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123 |
ourselves (this is unfortunately not done automatically by the MacOS event handling code). <p> |
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124 |
|
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125 |
<code>Do_idle</code> simply calls the TextEdit routine that blinks the cursor. <code>Getscrollbarvalues</code> |
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126 |
returns the current X and Y scrollbar values, scaled to <code>0..32767</code>. For X we return <code>None</code>, |
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127 |
which means "no scrollbar, please", for Y we use the scaler provided by <code>ScrolledWindow</code>. <p> |
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128 |
|
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129 |
<code>Scrollbar_callback</code> is called when the user uses the scrollbar. It is passed a string <code>'x'</code> |
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130 |
or <code>'y'</code>, one of <code>'set', '-', '--', '+', '++'</code> and (for <code>set</code>) an absolute |
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131 |
value. Note that the sign of the value passed to <code>TEPinScroll</code> is counter-intuitive. <p> |
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132 |
|
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133 |
<code>do_activate</code> (de)activates the scrollbars and calls the relevant TextEdit routine. Moreover, it |
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134 |
tells the application object if we are now the active window, and updates the menubar. The next few methods |
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135 |
are update and menu callbacks, and pretty straightforward. Note that <code>do_close</code> can |
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136 |
return without closing the window (if the document is changed and the users cancels out of the operation). |
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137 |
Also note the "magic" in <code>menu_save_as</code> |
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138 |
that set the correct window title. <p> |
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139 |
|
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140 |
Things get moderately interesting again at the cut/copy/paste handling, since the TextEdit scrap is |
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141 |
separate from the desktop scrap. For that reason there are various calls to routines that move the scrap |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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142 |
back and forth. <code>Have_selection</code> is called by the menubar update code to determine whether cut and |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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143 |
copy should be enabled. <p> |
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144 |
|
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145 |
Understanding the main program is left as an exercise to the reader. <p> |
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|
146 |
|
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147 |
<hr> |
|
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148 |
That's all for this example, you could now continue with the <A HREF="waste.html">next example</A>, where we use WASTE, a more-or-less |
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149 |
TextEdit compatible library with more functionality, to rebuild our editor. Or you can |
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150 |
return to the <A HREF="index.html">table of contents</A> to pick another topic. <p> |