layout/doc/debugtable.html

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  13 .log {background-color:silver; color:blue}
  14 pre.log {display:table-cell}
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  16
  17   <title>Debugging facilities in HTML-Table code</title>
  18 </head>
  19 <body>
  20  <h1>Debugging facilities in HTML-table code</h1>
  21  <h2>Reflow</h2>
  22  <p>The most efficient tool to claim that html-table code is the victim and not the source of layout bugs is a  <a href="http://lxr.mozilla.org/seamonkey/source/layout/doc/frame_reflow_debug.html">frame reflow  debug log</a>.  Look there especially how the maxElementsize (MES)  and desired size are propagated.
  23
  24  <h2>Block Reflow</h2>
  25 <p>
  26 Another way to debug the reflow process is implemented inside <a href="http://lxr.mozilla.org/seamonkey/source/layout/html/base/src/nsBlockFrame.cpp">nsBlockFrame.cpp</a>. It can be invoked by<p>
  27 <code>set GECKO_BLOCK_DEBUG_FLAGS=reflow</code>
  28 <p>
  29 The available options are:
  30 <ul>
  31 <li><code>reflow</code>
  32 <li> <code>really-noisy-reflow</code>
  33 <li><code>max-element-size</code>
  34 <li><code> space-manager</code>
  35 <li><code>verify-lines</code>
  36 <li><code>damage-repair</code>
  37 <li><code>lame-paint-metrics</code>
  38 <li><code>lame-reflow-metrics</code>
  39 <li><code>disable-resize-opt</code>
  40 </ul>
  41 <p>
  42 These options can be combined with a comma separated list
  43 Messages generated by the <code>reflow</code> switch:
  44 <ul>
  45 <li><code> Block(div)(1)@00BE5AC4: reflowing dirty lines computedWidth=9000 computedHeight=1500</code>
  46 <ul>
  47 <li> this message is generated inside of <br>
  48 <code>nsresult nsBlockFrame::ReflowDirtyLines(nsBlockReflowState& aState)</code>
  49 <li> it first shows the Block ID and Address
  50 <li>and then the computed width and Height from the HTMLReflowState.
  51 </ul>
  52 </ul>
  53
  54 <h2>DEBUG_TABLE_STRATEGY</h2>
  55 <p>
  56 The table layout strategy can be visualized by defining in the <a href="http://lxr.mozilla.org/seamonkey/source/layout/html/table/src/Makefile.in">makefiles</a> the constant DEBUG_TABLE_STRATEGY.
  57
  58 If one takes for instance the following table
  59 <table cellspacing="10"><tr><th>rendering</th><th>code</th></tr>
  60 <tr valign="top"><td valign="top" style="padding-top:10px">
  61 <table border width="300">
  62 <colgroup>
  63 <col>
  64 <col width="50%">
  65 <col width="1*">
  66 <col>
  67 </colgroup>
  68         <tr>
  69               <td style="width:80px">cell 1</td>
  70             <td>cell 2</td>
  71             <td>cell 3</td>
  72             <td>cell 4</td>
  73         </tr>
  74 </table>
  75 </td>
  76 <td valign="top"><pre class="log">
  77 &lt;table border width="300"&gt;
  78 &lt;colgroup&gt;
  79 &lt;col&gt;
  80 &lt;col width="50%"&gt;
  81 &lt;col width="1*"&gt;
  82 &lt;col&gt;
  83 &lt;/colgroup&gt;
  84         &lt;tr&gt;
  85               &lt;td style="width:80px"&gt;cell 1&lt;/td&gt;
  86             &lt;td&gt;cell 2&lt;/td&gt;
  87             &lt;td&gt;cell 3&lt;/td&gt;
  88             &lt;td&gt;cell 4&lt;/td&gt;
  89         &lt;/tr&gt;
  90 &lt;/table&gt;
  91 </pre>
  92 </td>
  93 </tr>
  94 </table>
  95 <p>
  96 it will produce the following log at the entrance of <code>AssignNonPctColWidths</code>:
  97 <p>
  98 <table class="log"><tr><td>
  99 <pre>
 100 AssignNonPctColWidths en max=4500 count=0
 101 ***START TABLE DUMP***
 102 mColWidths=-1 -1 -1 -1
 103
 104  col frame cache -&gt;
 105 0=00B93138 1=00B931F0 2=024DD728 3=024DD780
 106  **START COL DUMP** colIndex=0 isAnonymous=0 constraint=0
 107   widths=-1 -1 -1 -1 -1 -1 -1 -1 -1 -1  **END COL DUMP**
 108  **START COL DUMP** colIndex=1 isAnonymous=0 constraint=0
 109   widths=-1 -1 -1 -1 -1 -1 -1 -1 -1 -1  **END COL DUMP**
 110  **START COL DUMP** colIndex=2 isAnonymous=0 constraint=0
 111   widths=-1 -1 -1 -1 -1 -1 -1 -1 -1 -1  **END COL DUMP**
 112  **START COL DUMP** colIndex=3 isAnonymous=0 constraint=0
 113   widths=-1 -1 -1 -1 -1 -1 -1 -1 -1 -1  **END COL DUMP**
 114 ***END TABLE DUMP***
 115 </pre>
 116 </td></tr></table>
 117
 118
 119 <p>
 120 The <span class="log">en</span> stands for entrance (<span class="log">ex</span> for leaving a routine). The first line of the data dump shows that no width has yet been assigned to the columns <span class="log">mColWidths=-1 -1 -1 -1</span>,  <code>-1</code> stands for:
 121 <pre>
 122 #define WIDTH_NOT_SET   -1
 123 </pre>
 124 <p>
 125 This is followed by a reference to the column frame pointers:
 126 <p>
 127 <pre class="log">
 128 col frame cache -&gt;
 129 0=00B93138 1=00B931F0 2=024DD728 3=024DD780
 130 </pre>
 131 <p>
 132 This is followed by the information which width has been set for each column. The index of the column, whether it is anonymous and what kind of constrained has been applied<span class="log">colIndex=0 isAnonymous=0 constraint=0</span>. The following constraint types are known:
 133 <p>
 134 <pre>
 135   eNoConstraint          = 0,
 136   ePixelConstraint       = 1,      // pixel width
 137   ePercentConstraint     = 2,      // percent width
 138   eProportionConstraint  = 3,      // 1*, 2*, etc. cols attribute assigns 1*
 139   e0ProportionConstraint = 4       // 0*, means to force to min width
 140 </pre>
 141 <p>
 142 After this follows the width information for each column:
 143 <p>
 144 <pre class="log">
 145 widths=-1 -1 -1 -1 -1 -1 -1 -1 -1 -1
 146 </pre>
 147 <p>
 148 The table code knows ten different width's:
 149 <pre>
 150 #define NUM_WIDTHS       10
 151 #define NUM_MAJOR_WIDTHS 3 // MIN, DES, FIX
 152 #define MIN_CON          0 // minimum width required of the content + padding
 153 #define DES_CON          1 // desired width of the content + padding
 154 #define FIX              2 // fixed width either from the content or cell, col, etc. + padding
 155 #define MIN_ADJ          3 // minimum width + padding due to col spans
 156 #define DES_ADJ          4 // desired width + padding due to col spans
 157 #define FIX_ADJ          5 // fixed width + padding due to col spans
 158 #define PCT              6 // percent width of cell or col
 159 #define PCT_ADJ          7 // percent width of cell or col from percent colspan
 160 #define MIN_PRO          8 // desired width due to proportional &lt;col&gt;s or cols attribute
 161 #define FINAL            9 // width after the table has been balanced, considering all of the others
 162 </pre>
 163 <p>
 164 In the last log snippet none of these width's has been set.
 165 Leaving  AssignNonPctColWidths shows that already to all columns a width of 360 twips has been assigned
 166 <pre class="log">
 167 AssignNonPctColWidths ex
 168 ***START TABLE DUMP***
 169 mColWidths=360 360 360 360
 170
 171  col frame cache -&gt;
 172 0=00B93138 1=00B931F0 2=024DD728 3=024DD780
 173  **START COL DUMP** colIndex=0 isAnonymous=0 constraint=0
 174   widths=360 540 1230 -1 -1 -1 -1 -1 -1 360  **END COL DUMP**
 175  **START COL DUMP** colIndex=1 isAnonymous=0 constraint=0
 176   widths=360 540 -1 -1 -1 -1 -1 -1 -1 360  **END COL DUMP**
 177  **START COL DUMP** colIndex=2 isAnonymous=0 constraint=3
 178   widths=360 540 -1 -1 -1 -1 -1 -1 540 360  **END COL DUMP**
 179  **START COL DUMP** colIndex=3 isAnonymous=0 constraint=0
 180   widths=360 540 -1 -1 -1 -1 -1 -1 -1 360  **END COL DUMP**
 181 ***END TABLE DUMP***
 182 </pre>
 183 <p>
 184 The first column has already the minimum content width, the table column can't shrink below that, the desired content width of <span class="log">540</span> twips, that's the space to layout <code>cell 1</code> without wrapping the text and the <span class="log">1230</span> which correspond to the <code>style="width:80px"</code> at the first cell. At this step the final size is <span class="log">360</span> twips.
 185 <p>
 186 <table cellpadding="8">
 187 <tr>
 188 <th> MIN_CON</th><th>DES_CON</th><th>FIX</th><th>MIN_ADJ</th><th>DES_ADJ</th><th>FIX_ADJ</th><th>PCT</th><th> PCT_ADJ</th><th> MIN_PRO</th><th>FINAL</th>
 189 </tr>
 190 <tr align="center">
 191 <td>360</td><td> 540</td><td> 1230 </td><td>-1</td><td> -1 </td><td>-1</td><td> -1</td><td> -1</td><td> -1</td><td> 360</td></tr></table>
 192 <p>
 193 There was no change till the entrance of <code>BalanceColumnWidths
 194 </code>
 195 <p>
 196 <pre class="log">
 197 BalanceColumnWidths en count=1
 198 ***START TABLE DUMP***
 199 mColWidths=360 360 360 360
 200
 201  col frame cache -&gt;
 202 0=00B93138 1=00B931F0 2=024DD728 3=024DD780
 203  **START COL DUMP** colIndex=0 isAnonymous=0 constraint=0
 204   widths=360 540 1230 -1 -1 -1 -1 -1 -1 360  **END COL DUMP**
 205  **START COL DUMP** colIndex=1 isAnonymous=0 constraint=0
 206   widths=360 540 -1 -1 -1 -1 -1 -1 -1 360  **END COL DUMP**
 207  **START COL DUMP** colIndex=2 isAnonymous=0 constraint=3
 208   widths=360 540 -1 -1 -1 -1 -1 -1 540 360  **END COL DUMP**
 209  **START COL DUMP** colIndex=3 isAnonymous=0 constraint=0
 210   widths=360 540 -1 -1 -1 -1 -1 -1 -1 360  **END COL DUMP**
 211 ***END TABLE DUMP***
 212 </pre>
 213 <p>
 214 But at the end the final distribution between the columns has been reached.
 215 <p>
 216 <pre class="log">
 217 BalanceColumnWidths ex
 218 ***START TABLE DUMP***
 219 mColWidths=1230 2160 465 465
 220
 221  col frame cache -&gt;
 222 0=00B93138 1=00B931F0 2=024DD728 3=024DD780
 223  **START COL DUMP** colIndex=0 isAnonymous=0 constraint=0
 224   widths=360 540 1230 -1 -1 -1 -1 -1 -1 1230  **END COL DUMP**
 225  **START COL DUMP** colIndex=1 isAnonymous=0 constraint=0
 226   widths=360 540 -1 -1 -1 -1 2160 -1 -1 2160  **END COL DUMP**
 227  **START COL DUMP** colIndex=2 isAnonymous=0 constraint=3
 228   widths=360 540 -1 -1 -1 -1 -1 -1 540 465  **END COL DUMP**
 229  **START COL DUMP** colIndex=3 isAnonymous=0 constraint=0
 230   widths=360 540 -1 -1 -1 -1 -1 -1 -1 465  **END COL DUMP**
 231 ***END TABLE DUMP***
 232 </pre>
 233 <p>
 234 The column dump is implemented in <code>nsTableColFrame.cpp</code> in the routine:
 235 <code>void nsTableColFrame::Dump(int32_t aIndent)</code>.
 236
 237 <h2>DEBUG_TABLE_REFLOW_TIMING</h2>
 238 <p>needs to be written
 239
 240 <hr>
 241 <p style="text-align:right">author: Bernd Mielke <br>2002-06-05</p>
 242
 243 </body>
 244
 245 </html>