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Add accents

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Summary:
Add support for math-mode accents. This involves a couple changes.
First, in order to correctly position the accents, we must know the kern between
every character and the "skewchar" in that font. To do this, we improve our tfm
parser to run the mini-kern-language and calculate kerns. We then export these
into fontMetrics.js.

Then, we add normal support for accents. In particular, we do some special
handling for supsubs around accents. This involves building the supsub
separately without the accent, and then replacing its base with the built
accent.

Finally, the character in the fonts for the \vec command is a combining unicode
character, so it is shifted to the left, but none of the other characters do
this. We add some special handling for \vec to account for this.

Fixes #7

Test Plan:
 - Make sure tests pass
 - Make sure no huxley screenshots changed, and the new one looks good

Reviewers: alpert

Reviewed By: alpert

Differential Revision: http://phabricator.khanacademy.org/D13157
This commit is contained in:
Emily Eisenberg
2014-09-13 21:30:35 -07:00
parent 0d42a902ac
commit 0dca731da6
14 changed files with 340 additions and 33 deletions
Download Patch File Download Diff File Expand all files Collapse all files

26
metrics/extract_tfms.py
View File

@@ -34,6 +34,23 @@ def main():
'msbm10.tfm'
]
# Extracted by running `\font\a=<font>` and then `\showthe\skewchar\a` in
# TeX, where `<font>` is the name of the font listed here. The skewchar
# will be printed out in the output. If it outputs `-1`, that means there
# is no skewchar, so we use `None` here.
font_skewchar = {
'cmbsy10': None,
'cmbx10': None,
'cmex10': None,
'cmmi10': 127,
'cmmib10': None,
'cmr10': None,
'cmsy10': 48,
'cmti10': None,
'msam10': None,
'msbm10': None
}
font_name_to_tfm = {}
for font_name in fonts:
@@ -57,10 +74,17 @@ def main():
depth = round(tfm_char.depth - yshift / 1000.0, 5)
italic = round(tfm_char.italic_correction, 5)
skewkern = 0.0
if (font_skewchar[font] and
font_skewchar[font] in tfm_char.kern_table):
skewkern = round(
tfm_char.kern_table[font_skewchar[font]], 5)
families[family][char_num] = {
'height': height,
'depth': depth,
'italic': italic
'italic': italic,
'skew': skewkern,
}
sys.stdout.write(

2
metrics/extract_ttfs.py
View File

@@ -37,11 +37,13 @@ def main():
# TODO(emily): Figure out a real way to calculate this
italic = 0
skew = 0
start_json[font][ord(char)] = {
height: height / fontInfo.em,
depth: depth / fontInfo.em,
italic: italic / fontInfo.em,
skew: skew / fontInfo.em,
}
sys.stdout.write(

68
metrics/parse_tfm.py
View File

@@ -12,18 +12,48 @@ class CharInfoWord(object):
self.tag = b3 & 0b11
self.remainder = b4
def has_ligkern(self):
return self.tag == 1
def ligkern_start(self):
return self.remainder
class LigKernProgram(object):
def __init__(self, program):
self.program = program
def execute(self, start, next_char):
curr_instruction = start
while True:
instruction = self.program[curr_instruction]
(skip, inst_next_char, op, remainder) = instruction
if inst_next_char == next_char:
if op < 128:
# Don't worry about ligatures for now, we only need kerns
return None
else:
return 256 * (op - 128) + remainder
elif skip >= 128:
return None
else:
curr_instruction += 1 + skip
class TfmCharMetrics(object):
def __init__(self, width, height, depth, italic):
def __init__(self, width, height, depth, italic, kern_table):
self.width = width
self.height = height
self.depth = depth
self.italic_correction = italic
self.kern_table = kern_table
class TfmFile(object):
def __init__(self, start_char, end_char, char_info, width_table,
height_table, depth_table, italic_table):
height_table, depth_table, italic_table, ligkern_table,
kern_table):
self.start_char = start_char
self.end_char = end_char
self.char_info = char_info
@@ -31,6 +61,8 @@ class TfmFile(object):
self.height_table = height_table
self.depth_table = depth_table
self.italic_table = italic_table
self.ligkern_program = LigKernProgram(ligkern_table)
self.kern_table = kern_table
def get_char_metrics(self, char_num):
if char_num < self.start_char or char_num > self.end_char:
@@ -38,11 +70,19 @@ class TfmFile(object):
info = self.char_info[char_num + self.start_char]
char_kern_table = {}
if info.has_ligkern():
for char in range(self.start_char, self.end_char + 1):
kern = self.ligkern_program.execute(info.ligkern_start(), char)
if kern:
char_kern_table[char] = self.kern_table[kern]
return TfmCharMetrics(
self.width_table[info.width_index],
self.height_table[info.height_index],
self.depth_table[info.depth_index],
self.italic_table[info.italic_index])
self.italic_table[info.italic_index],
char_kern_table)
class TfmReader(object):
@@ -96,10 +136,8 @@ def read_tfm_file(file_name):
depth_table_size = reader.read_halfword()
italic_table_size = reader.read_halfword()
# ligkern_table_size
reader.read_halfword()
# kern_table_size
reader.read_halfword()
ligkern_table_size = reader.read_halfword()
kern_table_size = reader.read_halfword()
# extensible_table_size
reader.read_halfword()
@@ -142,8 +180,22 @@ def read_tfm_file(file_name):
for i in range(italic_table_size):
italic_table.append(reader.read_fixword())
ligkern_table = []
for i in range(ligkern_table_size):
skip = reader.read_byte()
next_char = reader.read_byte()
op = reader.read_byte()
remainder = reader.read_byte()
ligkern_table.append((skip, next_char, op, remainder))
kern_table = []
for i in range(kern_table_size):
kern_table.append(reader.read_fixword())
# There is more information, like the ligkern, kern, extensible, and
# param table, but we don't need these for now
return TfmFile(start_char, end_char, char_info, width_table,
height_table, depth_table, italic_table)
height_table, depth_table, italic_table,
ligkern_table, kern_table)