layout/style/generate-stylestructlist.py

   1 #!/usr/bin/env python
   2
   3 # This Source Code Form is subject to the terms of the Mozilla Public
   4 # License, v. 2.0. If a copy of the MPL was not distributed with this
   5 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
   6
   7 # This script generates nsStyleStructList.h, which contains macro invocations
   8 # that can be used for three things:
   9 #
  10 # 1. To generate code for each inherited style struct.
  11 # 2. To generate code for each reset style struct.
  12 # 3. To generate a tree of nested if statements that can be used to run
  13 #    some code on each style struct.
  14 #
  15 # As an example, if we assume that we have only four style structs, the
  16 # generated tree of nested if statements looks like this:
  17 #
  18 #   if (STYLE_STRUCT_TEST < 4) {
  19 #     if (STYLE_STRUCT_TEST < 2) {
  20 #       if (STYLE_STRUCT_TEST == 0) {
  21 #         ... code for style struct with id 0 ...
  22 #       } else {
  23 #         ... code for style struct with id 1 ...
  24 #       }
  25 #     } else {
  26 #       if (STYLE_STRUCT_TEST == 2) {
  27 #         ... code for style struct with id 2 ...
  28 #       } else {
  29 #         ... code for style struct with id 3 ...
  30 #       }
  31 #     }
  32 #   }
  33 #
  34 # The TOPLEVELBRANCHES variable controls how widely we branch on the outermost
  35 # if statement.  In the example above, it splits the search space in 2, but with
  36 # a larger number of style structs to test -- particularly when the number is
  37 # closer to one power of two than the next higher one -- the average number of
  38 # comparisons can be reduced by splitting the top level check into more than 2.
  39
  40 import math
  41
  42 # List of style structs and their corresponding Check callback functions,
  43 # if any.
  44 STYLE_STRUCTS = [("INHERITED",) + x for x in [
  45     # Inherited style structs.
  46     ("Font",           "CheckFontCallback"),
  47     ("Color",          "CheckColorCallback"),
  48     ("List",           "nullptr"),
  49     ("Text",           "CheckTextCallback"),
  50     ("Visibility",     "nullptr"),
  51     ("Quotes",         "nullptr"),
  52     ("UserInterface",  "nullptr"),
  53     ("TableBorder",    "nullptr"),
  54     ("SVG",            "nullptr"),
  55     ("Variables",      "CheckVariablesCallback"),
  56 ]] + [("RESET",) + x for x in [
  57     # Reset style structs.
  58     ("Background",     "nullptr"),
  59     ("Position",       "nullptr"),
  60     ("TextReset",      "nullptr"),
  61     ("Display",        "nullptr"),
  62     ("Content",        "nullptr"),
  63     ("UIReset",        "nullptr"),
  64     ("Table",          "nullptr"),
  65     ("Margin",         "nullptr"),
  66     ("Padding",        "nullptr"),
  67     ("Border",         "nullptr"),
  68     ("Outline",        "nullptr"),
  69     ("XUL",            "nullptr"),
  70     ("SVGReset",       "nullptr"),
  71     ("Column",         "nullptr"),
  72 ]]
  73
  74 # How widely to branch on the outermost if statement.
  75 TOPLEVELBRANCHES = 4
  76
  77
  78 # ---- Generate nsStyleStructList.h ----
  79
  80 count = len(STYLE_STRUCTS)
  81
  82 def nextPowerOf2(x):
  83     return int(pow(2, math.ceil(math.log(x, 2))))
  84
  85 def printEntry(i):
  86     print "STYLE_STRUCT_%s(%s, %s)" % STYLE_STRUCTS[i]
  87
  88 def printTestTree(min, max, depth, branches):
  89     indent = "  " * depth
  90     if min == count - 1 and max >= count:
  91         print "  STYLE_STRUCT_TEST_CODE(%sNS_ASSERTION(STYLE_STRUCT_TEST == %d, \"out of range\");)" % (indent, min)
  92         printEntry(min)
  93     elif max - min == 2:
  94         print "  STYLE_STRUCT_TEST_CODE(%sif (STYLE_STRUCT_TEST == %d) {)" % (indent, min)
  95         printEntry(min)
  96         print "  STYLE_STRUCT_TEST_CODE(%s} else {)" % indent
  97         printEntry(min + 1)
  98         print "  STYLE_STRUCT_TEST_CODE(%s})" % indent
  99     elif min < count:
 100         mid = min + (max - min) / branches
 101         print "  STYLE_STRUCT_TEST_CODE(%sif (STYLE_STRUCT_TEST < %d) {)" % (indent, mid)
 102         printTestTree(min, mid, depth + 1, 2)
 103         for branch in range(1, branches):
 104             lo = min + branch * (max - min) / branches
 105             hi = min + (branch + 1) * (max - min) / branches
 106             if lo >= count:
 107                 break
 108             if branch == branches - 1 or hi >= count:
 109                 print "  STYLE_STRUCT_TEST_CODE(%s} else {)" % indent
 110             else:
 111                 print "  STYLE_STRUCT_TEST_CODE(%s} else if (STYLE_STRUCT_TEST < %d) {)" % (indent, hi)
 112             printTestTree(lo, hi, depth + 1, 2)
 113         print "  STYLE_STRUCT_TEST_CODE(%s})" % indent
 114
 115 HEADER = """/* THIS FILE IS AUTOGENERATED BY generate-stylestructlist.py - DO NOT EDIT */
 116
 117 // IWYU pragma: private, include "nsStyleStructFwd.h"
 118
 119 /*
 120  * list of structs that contain the data provided by nsStyleContext, the
 121  * internal API for computed style data for an element
 122  */
 123
 124 /*
 125  * This file is intended to be used by different parts of the code, with
 126  * the STYLE_STRUCT macro (or the STYLE_STRUCT_INHERITED and
 127  * STYLE_STRUCT_RESET pair of macros) defined in different ways.
 128  */
 129
 130 #ifndef STYLE_STRUCT_INHERITED
 131 #define STYLE_STRUCT_INHERITED(name, checkdata_cb) \\
 132   STYLE_STRUCT(name, checkdata_cb)
 133 #define UNDEF_STYLE_STRUCT_INHERITED
 134 #endif
 135
 136 #ifndef STYLE_STRUCT_RESET
 137 #define STYLE_STRUCT_RESET(name, checkdata_cb) \\
 138   STYLE_STRUCT(name, checkdata_cb)
 139 #define UNDEF_STYLE_STRUCT_RESET
 140 #endif
 141
 142 #ifdef STYLE_STRUCT_TEST
 143 #define STYLE_STRUCT_TEST_CODE(c) c
 144 #else
 145 #define STYLE_STRUCT_TEST_CODE(c)
 146 #endif
 147
 148 // The inherited structs are listed before the Reset structs.
 149 // nsStyleStructID assumes this is the case, and callers other than
 150 // nsStyleStructFwd.h that want the structs in id-order just define
 151 // STYLE_STRUCT rather than including the file twice.
 152
 153 """
 154 FOOTER = """
 155 #ifdef UNDEF_STYLE_STRUCT_INHERITED
 156 #undef STYLE_STRUCT_INHERITED
 157 #undef UNDEF_STYLE_STRUCT_INHERITED
 158 #endif
 159
 160 #ifdef UNDEF_STYLE_STRUCT_RESET
 161 #undef STYLE_STRUCT_RESET
 162 #undef UNDEF_STYLE_STRUCT_RESET
 163 #endif
 164
 165 #undef STYLE_STRUCT_TEST_CODE
 166 """
 167
 168 print HEADER
 169 printTestTree(0, nextPowerOf2(count), 0, TOPLEVELBRANCHES)
 170 print FOOTER