Add support for canvas and multipart

Quite incomplete canvas implementation. Crucially, the layout engine
can't do much with whatever is drawn because it doesn't support images
yet.

I've re-introduced multipart as well, with the FormData API. For the
append function I've also introduced a hack to the JS binding generator
that allows requesting the JSContext pointer in nim procs. Really I
should just fix the union generator thing and add support for overloading.

In conclusion, for now the only thing canvas can be used for is exporting
it as PNG and uploading it somewhere. Also, we now have PNG encoding and
decoding too. (Now if only we had sixels as well...)

1 files changed, 50 insertions, 44 deletions

diff --git a/src/utils/twtstr.nim b/src/utils/twtstr.nim
index d67e1ab7..93fce06f 100644
--- a/src/utils/twtstr.nim
+++ b/src/utils/twtstr.nim
@@ -122,6 +122,11 @@ func snakeToKebabCase*(str: string): string =
     if c == '_':
       c = '-'
 
+func normalizeLocale*(s: string): string =
+  for i in 0 ..< s.len:
+    if cast[uint8](s[i]) > 0x20 and s[i] != '_' and s[i] != '-':
+      result &= s[i].toLowerAscii()
+
 func isAscii*(r: Rune): bool =
   return cast[uint32](r) < 128
 
@@ -168,6 +173,9 @@ func toHex*(c: char): string =
   result[0] = HexChars[(uint8(c) shr 4)]
   result[1] = HexChars[(uint8(c) and 0xF)]
 
+func toHex*(i: uint8): string =
+  return toHex(cast[char](i))
+
 func equalsIgnoreCase*(s1: seq[Rune], s2: string): bool =
   var i = 0
   while i < min(s1.len, s2.len):
@@ -236,6 +244,17 @@ func after*(s: string, c: set[char]): string =
 
 func after*(s: string, c: char): string = s.after({c})
 
+func afterLast*(s: string, c: set[char], n = 1): string =
+  var j = 0
+  for i in countdown(s.high, 0):
+    if s[i] in c:
+      inc j
+      if j == n:
+        return s.substr(i + 1)
+  return s
+
+func afterLast*(s: string, c: char, n = 1): string = s.afterLast({c}, n)
+
 proc c_sprintf(buf, fm: cstring): cint {.header: "<stdio.h>", importc: "sprintf", varargs}
 
 # From w3m
@@ -345,72 +364,59 @@ func japaneseNumber*(i: int): string =
     result &= ss[n]
     dec n
 
-func parseInt32*(s: string): int =
-  var sign = 1
-  var t = 1
-  var integer: int = 0
-  var e: int = 0
-
+# Implements https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#signed-integers
+#TODO TODO TODO handle overflow defects
+func parseInt32*(s: string): Option[int32] =
+  var sign: int32 = 1
   var i = 0
   if i < s.len and s[i] == '-':
     sign = -1
     inc i
   elif i < s.len and s[i] == '+':
     inc i
-
+  if i == s.len or s[i] notin AsciiDigit:
+    return none(int32)
+  var integer = int32(decValue(s[i]))
+  inc i
   while i < s.len and isDigit(s[i]):
     integer *= 10
-    integer += decValue(s[i])
+    integer += int32(decValue(s[i]))
     inc i
+  return some(sign * integer)
 
-  if i < s.len and (s[i] == 'e' or s[i] == 'E'):
-    inc i
-    if i < s.len and s[i] == '-':
-      t = -1
-      inc i
-    elif i < s.len and s[i] == '+':
-      inc i
-
-    while i < s.len and isDigit(s[i]):
-      e *= 10
-      e += decValue(s[i])
-      inc i
-
-  return sign * integer * 10 ^ (t * e)
-
-func parseInt64*(s: string): int64 =
-  var sign = 1
-  var t = 1
-  var integer: int64 = 0
-  var e: int64 = 0
-
+func parseInt64*(s: string): Option[int64] =
+  var sign: int64 = 1
   var i = 0
   if i < s.len and s[i] == '-':
     sign = -1
     inc i
   elif i < s.len and s[i] == '+':
     inc i
-
+  if i == s.len or s[i] notin AsciiDigit:
+    return none(int64)
+  var integer = int64(decValue(s[i]))
+  inc i
   while i < s.len and isDigit(s[i]):
     integer *= 10
-    integer += decValue(s[i])
+    integer += int64(decValue(s[i]))
     inc i
+  return some(sign * integer)
 
-  if i < s.len and (s[i] == 'e' or s[i] == 'E'):
+func parseUInt32*(s: string): Option[uint32] =
+  var i = 0
+  if i < s.len and s[i] == '+':
     inc i
-    if i < s.len and s[i] == '-':
-      t = -1
-      inc i
-    elif i < s.len and s[i] == '+':
-      inc i
-
-    while i < s.len and isDigit(s[i]):
-      e *= 10
-      e += decValue(s[i])
-      inc i
-
-  return sign * integer * 10 ^ (t * e)
+  if i == s.len or s[i] notin AsciiDigit:
+    return none(uint32)
+  var integer = uint32(decValue(s[i]))
+  inc i
+  while i < s.len and isDigit(s[i]):
+    integer *= 10
+    integer += uint32(decValue(s[i]))
+    inc i
+  return some(integer)
 
+#TODO not sure where this algorithm is from...
 func parseFloat64*(s: string): float64 =
   var sign = 1
   var t = 1