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, 28 insertions, 82 deletions

diff --git a/src/buffer/buffer.nim b/src/buffer/buffer.nim
index 7fda2887..d668a01d 100644
--- a/src/buffer/buffer.nim
+++ b/src/buffer/buffer.nim
@@ -40,9 +40,11 @@ import render/rendertext
 import types/buffersource
 import types/color
 import types/cookie
+import types/formdata
 import types/referer
 import types/url
 import utils/twtstr
+import xhr/formdata as formdata_impl
 
 type
   LoadInfo* = enum
@@ -751,82 +753,19 @@ proc cancel*(buffer: Buffer): int {.proxy.} =
     buffer.do_reshape()
   return buffer.lines.len
 
-# https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#constructing-the-form-data-set
-proc constructEntryList(form: HTMLFormElement, submitter: Element = nil, encoding: string = ""): seq[tuple[name, value: string]] =
-  if form.constructingentrylist:
-    return
-  form.constructingentrylist = true
-
-  var entrylist: seq[tuple[name, value: string]]
-  for field in form.controls:
-    if field.findAncestor({TAG_DATALIST}) != nil or
-        field.attrb("disabled") or
-        field.isButton() and Element(field) != submitter:
-      continue
-
-    if field.tagType == TAG_INPUT:
-      let field = HTMLInputElement(field)
-      if field.inputType == INPUT_IMAGE:
-        let name = if field.attr("name") != "":
-          field.attr("name") & '.'
-        else:
-          ""
-        entrylist.add((name & 'x', $field.xcoord))
-        entrylist.add((name & 'y', $field.ycoord))
-        continue
-
-    #TODO custom elements
-
-    let name = field.attr("name")
-
-    if name == "":
-      continue
-
-    if field.tagType == TAG_SELECT:
-      let field = HTMLSelectElement(field)
-      for option in field.options:
-        if option.selected or option.disabled:
-          entrylist.add((name, option.value))
-    elif field.tagType == TAG_INPUT and HTMLInputElement(field).inputType in {INPUT_CHECKBOX, INPUT_RADIO}:
-      let value = if field.attr("value") != "":
-        field.attr("value")
-      else:
-        "on"
-      entrylist.add((name, value))
-    elif field.tagType == TAG_INPUT and HTMLInputElement(field).inputType == INPUT_FILE:
-      #TODO file
-      discard
-    elif field.tagType == TAG_INPUT and HTMLInputElement(field).inputType == INPUT_HIDDEN and name.equalsIgnoreCase("_charset_"):
-      let charset = if encoding != "":
-        encoding
-      else:
-        "UTF-8"
-      entrylist.add((name, charset))
-    else:
-      case field.tagType
-      of TAG_INPUT:
-        entrylist.add((name, HTMLInputElement(field).value))
-      of TAG_BUTTON:
-        entrylist.add((name, HTMLButtonElement(field).value))
-      of TAG_TEXTAREA:
-        entrylist.add((name, HTMLTextAreaElement(field).value))
-      else: assert false, "Tag type " & $field.tagType & " not accounted for in constructEntryList"
-    if field.tagType == TAG_TEXTAREA or
-        field.tagType == TAG_INPUT and HTMLInputElement(field).inputType in {INPUT_TEXT, INPUT_SEARCH}:
-      if field.attr("dirname") != "":
-        let dirname = field.attr("dirname")
-        let dir = "ltr" #TODO bidi
-        entrylist.add((dirname, dir))
-
-  form.constructingentrylist = false
-  return entrylist
-
 #https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#multipart/form-data-encoding-algorithm
-proc serializeMultipartFormData(kvs: seq[(string, string)]): MimeData =
-  for it in kvs:
-    let name = makeCRLF(it[0])
-    let value = makeCRLF(it[1])
-    result[name] = value
+proc serializeMultipartFormData(entries: seq[FormDataEntry]): FormData =
+  {.cast(noSideEffect).}:
+    # This is correct, because newFormData with no params has no side effects.
+    let formData = newFormData()
+    for entry in entries:
+      let name = makeCRLF(entry.name)
+      if entry.isstr:
+        let value = makeCRLF(entry.svalue)
+        formData.append(name, value)
+      else:
+        formData.append(name, entry.value, entry.filename)
+    return formData
 
 proc serializePlainTextFormData(kvs: seq[(string, string)]): string =
   for it in kvs:
@@ -837,7 +776,9 @@ proc serializePlainTextFormData(kvs: seq[(string, string)]): string =
     result &= "\r\n"
 
 func submitForm(form: HTMLFormElement, submitter: Element): Option[Request] =
-  let entrylist = form.constructEntryList(submitter)
+  if form.constructingEntryList:
+    return
+  let entrylist = form.constructEntryList(submitter).get(@[])
 
   let action = if submitter.action() == "":
     $form.document.url
@@ -868,25 +809,30 @@ func submitForm(form: HTMLFormElement, submitter: Element): Option[Request] =
   #let noopener = true #TODO
 
   template mutateActionUrl() =
-    let query = serializeApplicationXWWWFormUrlEncoded(entrylist)
+    let kvlist = entrylist.toNameValuePairs()
+    let query = serializeApplicationXWWWFormUrlEncoded(kvlist)
     parsedaction.query = query.some
     return newRequest(parsedaction, httpmethod).some
 
   template submitAsEntityBody() =
     var mimetype: string
     var body = none(string)
-    var multipart = none(MimeData)
+    var multipart = none(FormData)
     case enctype
     of FORM_ENCODING_TYPE_URLENCODED:
-      body = serializeApplicationXWWWFormUrlEncoded(entrylist).some
+      let kvlist = entrylist.toNameValuePairs()
+      body = some(serializeApplicationXWWWFormUrlEncoded(kvlist))
       mimeType = $enctype
     of FORM_ENCODING_TYPE_MULTIPART:
-      multipart = serializeMultipartFormData(entrylist).some
+      multipart = some(serializeMultipartFormData(entrylist))
       mimetype = $enctype
     of FORM_ENCODING_TYPE_TEXT_PLAIN:
-      body = serializePlainTextFormData(entrylist).some
+      let kvlist = entrylist.toNameValuePairs()
+      body = some(serializePlainTextFormData(kvlist))
       mimetype = $enctype
-    return newRequest(parsedaction, httpmethod, @{"Content-Type": mimetype}, body).some #TODO multipart
+    let req = newRequest(parsedaction, httpmethod,
+      @{"Content-Type": mimetype}, body)
+    return some(req) #TODO multipart
 
   template getActionUrl() =
     return newRequest(parsedaction).some