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| 3 | href="eclipseos2-xxe.css"
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| 7 | <html>
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| 8 | <head>
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| 9 | <link href="eclipseos2.css" rel="stylesheet" type="text/css" />
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| 10 |
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| 11 | <title>Eclipse for OS/2 Transitional Project Notes</title>
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| 12 | </head>
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| 13 |
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| 14 | <body>
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| 15 | <h1>SWT Step 7. Buttons</h1>
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| 16 |
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| 17 | <h2>Objective</h2>
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| 18 |
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| 19 | <p>Complete the implementation of the <code>o.e.swt.widgets.Button</code>
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| 20 | widget. The test example should demonstrate all types of buttons that
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| 21 | exist in SWT.</p>
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| 22 |
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| 23 | <h2>Task notes</h2>
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| 24 |
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| 25 | <p>Button text and icon alignment styles (<code>SWT.LEFT</code>,
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| 26 | <code>SWT.RIGHT</code>, <code>SWT.CENTER</code>) are not currently
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| 27 | supported. I personally see no need in these styles at all. Besides this,
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| 28 | supporting them will make it impossible to keep the system look and feel
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| 29 | for <code>SWT.PUSH</code> buttons (for example, provided by eStyler).</p>
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| 30 |
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| 31 | <p>However, <code>SWT.TOGGLE</code> buttons currently lose the pushbutton
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| 32 | L&F provided by eStyler in any case, since they are completely drawn
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| 33 | by hand due to lack of this type of buttons in OS/2. We're in contact with
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| 34 | the eStyler author and hope this will be worked around later.</p>
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| 35 |
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| 36 | <p>When implementing this step, it turned out that some other
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| 37 | functionality has to be implemented within it, and something needs to be
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| 38 | changed. In particular, the following has been additionally
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| 39 | implemented:</p>
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| 40 |
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| 41 | <ul>
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| 42 | <li>keyboard handling (<code>SWT.KeyDown</code>/<code>KeyUp</code>
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| 43 | events)</li>
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| 44 |
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| 45 | <li>focus traversal (<code>SWT.FocusIn</code>/<code>FocusOut</code>)
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| 46 | using the keyboard (<kbd>TAB</kbd>/<kbd>Shift-TAB</kbd>, arrows,
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| 47 | mnemonic keys [with and w/o the <kbd>Alt</kbd> key])</li>
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| 48 |
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| 49 | <li>shell activation/deactivation
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| 50 | (<code>SWT.Activate</code>/<code>Deactivate</code>)</li>
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| 51 | </ul>
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| 52 |
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| 53 | <p>Also, it became necessary to change the <code>Decorations</code>
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| 54 | implementation.</p>
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| 55 |
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| 56 | <p>The following subsections provide some further details.</p>
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| 57 |
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| 58 | <h4>keyboard handling</h4>
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| 59 |
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| 60 | <p>The current implementation of keyboard events is very simple: OS/2
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| 61 | virtual keys supported by Eclipse are reported as Eclipse virtual keys
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| 62 | (<code>KeyEvent::keyCode</code>) with <code>KeyEvent::character</code> set
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| 63 | to zero. All other events have <code>keyCode</code> set to zero and
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| 64 | <code>character</code> equal to what OS/2 reports in the <code>usch</code>
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| 65 | parameter of the <code>WM_CHAR</code> message (converted to unicode
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| 66 | according to the curent locale), except the situation when both
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| 67 | <code>keyCode</code> and <code>character</code> are zero (no
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| 68 | <code>KeyEvent</code> is generated in this case).</p>
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| 69 |
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| 70 | <p>This differs a bit from how Eclipse/Win32 generates key events. For
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| 71 | example, when we press <kbd>Ctrl</kbd> and then press and release the
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| 72 | <kbd>A</kbd> key, Eclipse/OS2 reports <kbd>a</kbd> (<code>0x71</code>) in
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| 73 | the <code>character</code> field of the key press event and the control
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| 74 | code <code>0x11</code> in the same field of the key release event (i.e.
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| 75 | key press character doesn't match key release character); Win32 reports
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| 76 | <code>0x11</code> in both cases. Another example is <kbd>Alt</kbd> plus
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| 77 | letter. Eclipse/OS2 doesn't generate the key release event for the letter
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| 78 | at all, since <code>usch</code> in <code>WM_CHAR</code> is zero in this
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| 79 | case (Win32 reports both).</p>
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| 80 |
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| 81 | <p>The reason why I left the OS/2 behavior as is for now (i.e. not fully
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| 82 | compatible with Win32) is simple: currently, I don't get the logic how
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| 83 | keyboard messages are handled in Win32. For example, if you press
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| 84 | <kbd>Alt</kbd> there, then press some letter, then release <kbd>Alt</kbd>
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| 85 | and finally release the letter you get three events: a press event with
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| 86 | <code>keyCode=SWT.ALT</code> and <code>character=0</code>, a press event
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| 87 | with <code>keyCode=0</code> and <code>character=<letter></code>, and
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| 88 | a combined release event with <code>keyCode=SWT.ALT</code> and
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| 89 | <code>character=<letter></code> (i.e. we also get press/release pair
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| 90 | mismatch) -- that seems strage to me. But all this is related to the
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| 91 | pretty outdated SWT version 2.01, and I think things have changed in
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| 92 | recent SWT/Win32 releases, so the keyboard handling in Eclipse/OS2 will be
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| 93 | improved later, when we move the whole project to one of current Eclipse
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| 94 | releases.</p>
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| 95 |
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| 96 | <h4>Decorations reimplementation</h4>
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| 97 |
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| 98 | <p>The previous <code>Decorations</code> <a
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| 99 | href="swt003.html#FrameClientWindow">implementation</a> involved a special
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| 100 | internal SWT widget (<code>ClientArea</code>) to represent the client area
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| 101 | of any top-level window. This caused lots of problems related (not only)
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| 102 | to focus traversal because of the explicitly expressed parent-child
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| 103 | relationship (on SWT level) between the frame and client window
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| 104 | (<code>ClientArea</code> was created as a child of
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| 105 | <code>Decorations</code>, both in OS/2 and in SWT terms). This broke the
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| 106 | children-related functionality in SWT and led to some other issues.</p>
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| 107 |
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| 108 | <p>So, I chose a bit different solution. Instead of having a special SWT
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| 109 | class for the client area, <code>Decorations</code> now maintains two
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| 110 | window handles directly -- one is a regular <code>Control::handle</code>
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| 111 | field that now holds a handle to the client window (not a frame window
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| 112 | handle as before), and another one is a separate field,
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| 113 | <code>Decorations::frameHandle</code>, to hold the frame window
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| 114 | (<code>WC_FRAME</code>) handle. Both windows are created by
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| 115 | <code>Decorations::createHandle()</code>. The majority of new or overriden
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| 116 | <code>Decorations</code> methods use the <code>frameHandle</code> field,
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| 117 | while methods derived from <code>Composite</code>, <code>Control</code>
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| 118 | etc. continue to use the <code>handle</code> field. Also, PM message
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| 119 | handling was explicitely separated: <code>Decorations</code> has an
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| 120 | additional window procedure, <code>windowFrameProc()</code>, that delivers
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| 121 | messages addressed to the <code>WC_FRAME</code> window to
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| 122 | <code>Decoration</code>'s methods. These methods are named
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| 123 | <code>FRAME_WM_*</code> to differ from regular <code>WM_*</code> messages
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| 124 | processed by <code>windowProc()</code> as usual.</p>
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| 125 |
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| 126 | <p>The <code>ClientArea</code> class has been completely removed.</p>
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| 127 | </body>
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| 128 | </html>
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