~ubuntu-branches/ubuntu/precise/kompozer/precise

<p> The frame reflow can be logged with the debug capabilties implemented in <a href="http://lxr.mozilla.org/seamonkey/source/layout/html/base/src/nsFrame.cpp"><code>nsFrame.cpp</code></a>.

It provides the following information for each frame at the

start of its reflow

<ul>

<li>reflow reason

<li>available width, available height

<li>computed width, computed height

<li>the previous and the next frame in flow

<li>and a count number.

</ul>

<p>When the frame's reflow is finished the following information is displayed :</p>

<ul>

<li>reflow metric (desired) width, height

<li>max. element size (MES) width

<li>maximum Width

<li>frame status

<li>overflow area

</ul>

<h2>Getting the log</h2>

<ul>

<li>Make sure that your build is a <b>debug</b> build.

<li>Create a text file (for instance <code>reflow_rules.txt</code>).

<li>Enter this line in the text file <pre>* 1</pre>

<li>Save the text file in the <code>%DIST%</code> directory

<li>Go to the <code>%DIST%</code> directory

<li>enter from command line: <code>set GECKO_DISPLAY_REFLOW_RULES_FILE=reflow_rules.txt</code>

<li> Run <code>viewer > logfile.txt</code> and load your testcase. The

logfile will contain all the promised information.

</ul>

<h2>Log File analyis</h2>

<p>The logfile for a simple table like</p>

<pre>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

<head>

</head>

<body>

<tbody>

<tr>

</tr>

</tbody>

</table>

</body>

</html>

</pre>

<p> will create the following log:</p>

<pre>

VP 00B97C30 r=0 a=9180,4470 c=9180,4470 cnt=856

scroll 00B97EE0 r=0 a=9180,4470 c=9180,4470 cnt=857

scroll 00B97EE0 r=0 a=9180,4470 c=9180,4470 cnt=858

canvas 00B97C6C r=0 a=9180,UC c=9180,4470 cnt=859

area 02D7AFE4 r=0 a=9180,UC c=9180,UC cnt=860

text 02D7B150 r=0 a=9180,UC c=UC,UC cnt=861

text 02D7B150 d=0,0

block 02D7B210 r=0 a=9180,UC c=8940,UC cnt=862

block 02D7B210 d=8940,0

area 02D7AFE4 d=9180,120

canvas 00B97C6C d=9180,4470

scroll 00B97EE0 d=9180,4470

VP 00B97C30 d=9180,4470

VP 00B97C30 r=1 a=9180,4470 c=9180,4470 cnt=863

scroll 00B97EE0 r=1 a=9180,4470 c=9180,4470 cnt=864

scroll 00B97EE0 r=1 a=9180,4470 c=9180,4470 cnt=865

canvas 00B97C6C r=1 a=9180,UC c=9180,4470 cnt=866

area 02D7AFE4 r=1 a=9180,UC c=9180,UC cnt=867

block 02D7B210 r=1 a=9180,UC c=8940,UC cnt=868

text 02D7B3F8 r=0 a=8940,UC c=UC,UC cnt=869

text 02D7B3F8 d=0,0

tblO 02D7B5F0 r=0 a=8940,UC c=0,0 cnt=870

tbl 02D7B7EC r=0 a=8940,UC c=1500,UC cnt=871

rowG 00B984A4 r=0 a=UC,UC c=UC,UC cnt=872

row 02D7BAF8 r=0 a=UC,UC c=UC,UC cnt=873

cell 02D7BC98 r=0 a=UC,UC c=UC,UC cnt=874

block 02D7BCF8 r=0 a=UC,UC c=UC,UC cnt=875

text 02D7BE84 r=0 a=UC,UC c=UC,UC cnt=876

text 02D7BE84 d=300,285 me=300

block 02D7BCF8 d=300,300 me=300

cell 02D7BC98 d=330,330 me=330

row 02D7BAF8 d=UC,330

100

rowG 00B984A4 d=UC,330

101

colG 02D7BFB0 r=0 a=UC,UC c=UC,UC cnt=877

102

col 02D7C0D8 r=0 a=0,0 c=1500,UC cnt=878

103

col 02D7C0D8 d=0,0

104

colG 02D7BFB0 d=0,0

105

rowG 00B984A4 r=2 a=1500,UC c=1500,UC cnt=879

106

row 02D7BAF8 r=2 a=1500,UC c=1500,UC cnt=880

107

cell 02D7BC98 r=2 a=1440,UC c=1410,UC cnt=881

108

block 02D7BCF8 r=2 a=1410,UC c=1410,UC cnt=882

109

block 02D7BCF8 d=1410,300

110

cell 02D7BC98 d=1440,330

111

row 02D7BAF8 d=1500,330

112

rowG 00B984A4 d=1500,330

113

colG 02D7BFB0 r=2 a=1500,UC c=1500,UC cnt=883

114

col 02D7C0D8 r=0 a=0,0 c=1500,UC cnt=884

115

col 02D7C0D8 d=0,0

116

colG 02D7BFB0 d=0,0

117

tbl 02D7B7EC d=1500,390

118

tblO 02D7B5F0 d=1500,390

119

text 02D7C130 r=0 a=8940,UC c=UC,UC cnt=885

120

text 02D7C130 d=0,0

121

block 02D7B210 d=8940,390

122

area 02D7AFE4 d=9180,630

123

canvas 00B97C6C d=9180,4470

124

scroll 00B97EE0 d=9180,4470

125

scroll 00B97EE0 d=9180,4470

126

VP 00B97C30 d=9180,4470

127

</pre>

128

</td></tr></table>

129

<p>

130

The first line shows the reflow of the viewport (<code class="log">VP</code>). This viewport has the address <code class="log">00B97C30</code>. It is the initial reflow: <code class="log">r=0</code>. Other reflow reasons are: </p>

131

<table>

132

<tr><td>1</td><td>incremental reflow</td></tr>

133

<tr><td>2</td><td>resize reflow</td></tr>

134

<tr><td>3</td><td>style change reflow</td></tr>

135

<tr><td>4</td><td>dirty reflow.</td></tr>

136

</table>

137

138

<p>The available width is 9180 twips. The available height is 4470 twips (<code class="log">a=9180,4470</code>). The computed width is 9180 twips. The computed height is 4470 twips (<code class="log">c=9180,4470</code>). The line count is 856 (<code class="log">cnt=856</code>).

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<p>

140

Below this is a line that reads:<p><code class="log">tblO 02D7B5F0 r=0 a=8940,UC c=0,0 cnt=870</code></p><p> Here the <code class="log">UC</code> shows that on initial reflow the available height for the outer table frame is unconstrained.

141

<p>

142

The table cell requires its children to compute the MES. It is reported back from the block as:

143

<p><code class="log">block 02D7BCF8 d=300,300 me=300</code></p>

144

<p>The block max. element size is 300 twips.

145

<p> The second table reflow is started at

146

147

<p>where the previous information is used.

148

The block has been required to compute the max. element size only once and it reports now:

149

<p> <code class="log">block 02D7BCF8 d=1410,300</code></p>

150

<p>The block shows the same address as the previous one.

151

<p>Frames with children that overflow the parent have the <code>NS_FRAME_OUTSIDE_CHILDREN</code> flag set. For these frames

152

the overflowarea is displayed as <code class="log">block 025ED8F0 d=8940,1020 o=(0,0) 9180 x 1020</code>. The overflow area is specified as (x,y) origin and width x height.

153

<p> The reflow finishes at the same level where it started.

154

155

<h2>Advanced reflow debugging</h2>

156

<p>The previously described technique dumps the data for every frame. Sometimes the log is clearer if only the main frames are shown.

157

The entries in the reflow log can be controlled on a frame level. For instance adding <code>text 0</code> to the rules in <code>reflow_rules.txt</code> would hide the text entries from the reflow. The display of the following frames can be turned on by adding a line with the frame name and <code>1</code> or turned off by adding a line with the frame name and <code>0</code>:</p>

158

159

<tr><th style="text-align:left">short name</th><th style="text-align:left">layout tag</th></tr>

160

161

<tr><td>block</td><td>block</td></tr>

162

163

<tr><td>bullet</td><td>bullet</td></tr>

164

<tr><td>button</td><td>gfxButtonControl</td></tr>

165

166

<tr><td>frameI</td><td>htmlFrameInner</td></tr>

167

<tr><td>frameO</td><td>htmlFrameOuter</td></tr>

168

<tr><td>img</td><td>image</td></tr>

169

<tr><td>inline</td><td>inline</td></tr>

170

<tr><td>letter</td><td>letter</td></tr>

171

172

<tr><td>select</td><td>select</td></tr>

173

<tr><td>obj</td><td>object</td></tr>

174

175

<tr><td>place</td><td>placeholder</td></tr>

176

<tr><td>posInline</td><td>positionedInline</td></tr>

177

<tr><td>canvas</td><td>canvas</td></tr>

178

179

<tr><td>scroll</td><td>scroll</td></tr>

180

<tr><td>caption</td><td>tableCaption</td></tr>

181

<tr><td>cell</td><td>tableCell</td></tr>

182

<tr><td>bcCell</td><td>bcTableCell</td></tr>

183

<tr><td>col</td><td>tableCol</td></tr>

184

<tr><td>colG</td><td>tableColGroup</td></tr>

185

<tr><td> tbl</td><td>table</td></tr>

186

<tr><td>tblO</td><td>tableOuter</td></tr>

187

<tr><td>rowG</td><td>tableRowGroup</td></tr>

188

<tr><td>row</td><td>tableRow</td></tr>

189

<tr><td>textCtl</td><td>textInput</td></tr>

190

191

<tr><td>VP</td><td>viewport</td></tr>

192

</table>

193

<p>Once the problem is reduced to a single frame level, placing a breakpoint at <code>DisplayReflowEnterPrint</code> in <a href="http://lxr.mozilla.org/seamonkey/source/layout/html/base/src/nsFrame.cpp"><code>nsFrame.cpp</code></a> is a very efficient way to step through

194

the reflow tree.

195

196

<h2>Other reflow debug options</h2>

197

198

<h3>GECKO_DISPLAY_REFLOW_FLAG_PIXEL_ERRORS</h3>

199

<p>

200

Setting this option via <code>set GECKO_DISPLAY_REFLOW_FLAG_PIXEL_ERRORS = 1</code> enables a verification for each coordinate value that the coordinates are aligned at pixel boundaries.

201

202

<pre>

203

row 0268A594 r=0 a=UC,UC c=UC,20 cnt=870

204

VALUE 20 is not a whole pixel

205

cell 0268A6C0 r=0 a=UC,UC c=UC,15 cnt=871

206

block 0268A764 r=0 a=UC,UC c=UC,UC cnt=872

207

block 0268A764 d=0,0 me=0

208

cell 0268A6C0 d=0,0 me=0

209

row 0268A594 d=UC,20

210

VALUE 20 is not a whole pixel

211

rowG 0268A02C d=UC,695

212

VALUE 695 is not a whole pixel</pre>

213

</td></tr></table>

214

<p>

215

While unaligned values at the entrance of a frame reflow can be ignored, when they appear at the exit of a routine this can cause display errors like stray lines. OS2 is very vulnerable to pixel alignement errors as text is drawn on pixel boundaries.

216

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<h3>GECKO_DISPLAY_REFLOW_INDENT_UNDISPLAYED_FRAMES</h3>

218

<p>

219

Setting this option via <code>set GECKO_DISPLAY_REFLOW_INDENT_UNDISPLAYED_FRAMES = 1</code> will cause an advance of the indent even for frames which are blocked via the reflow rules file.

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</body>

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</html>

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