fix the flickering by delaying and throwing

Explanation coming on my blog, math2001.github.io, something like
"lessons learned from re writing MarkdownLivePreview"

MarkdownLivePreview.py

@@ -10,7 +10,7 @@ from .utils import *
 MARKDOWN_VIEW_INFOS = "markdown_view_infos"
 PREVIEW_VIEW_INFOS = "preview_view_infos"
 # FIXME: put this as a setting for the user to choose?
-DELAY = 500 # ms
+DELAY = 100 # ms
 
 def get_resource(resource):
     path = 'Packages/MarkdownLivePreview/resources/' + resource
@@ -102,6 +102,7 @@ class OpenMarkdownPreviewCommand(sublime_plugin.TextCommand):
         # FIXME: is this the best way there is to check if the current syntax is markdown?
         #        should we only support default markdown?
         #        what about "md"?
+        # FIXME: what about other languages, where markdown preview roughly works?
         return 'markdown' in self.view.settings().get('syntax').lower()
 
 class MarkdownLivePreviewListener(sublime_plugin.EventListener):
@@ -110,6 +111,10 @@ class MarkdownLivePreviewListener(sublime_plugin.EventListener):
         # markdown_view.id(): phantom set
     }
 
+    # we schedule an update for every key stroke, with a delay of DELAY
+    # then, we update only if now() - last_update > DELAY
+    last_update = 0
+
     # FIXME: maybe we shouldn't restore the file in the original window...
 
     def on_pre_close(self, markdown_view):
@@ -124,7 +129,6 @@ class MarkdownLivePreviewListener(sublime_plugin.EventListener):
         self.file_name = markdown_view.file_name()
 
         if self.file_name is None:
-            # FIXME: this is duplicated code. How should it be generalized?
             total_region = sublime.Region(0, markdown_view.size())
             self.content = markdown_view.substr(total_region)
             markdown_view.erase(edit, total_region)
@@ -180,22 +184,26 @@ class MarkdownLivePreviewListener(sublime_plugin.EventListener):
     # @min_time_between_call(.5)
     def on_modified_async(self, markdown_view):
 
-        # FIXME: it keeps on flickering, it's really annoying
-
         infos = markdown_view.settings().get(MARKDOWN_VIEW_INFOS)
         if not infos:
             return
 
-        self._update_preview(markdown_view)
+        # we schedule an update, which won't run if an 
+        sublime.set_timeout(partial(self._update_preview, markdown_view), DELAY)
 
     def _update_preview(self, markdown_view):
         # if the buffer id is 0, that means that the markdown_view has been closed
         # This check is needed since a this function is used as a callback for when images
         # are loaded from the internet (ie. it could finish loading *after* the user
         # closes the markdown_view)
+        if time.time() - self.last_update < DELAY / 1000:
+            return
+
         if markdown_view.buffer_id() == 0:
             return
 
+        self.last_update = time.time()
+
         total_region = sublime.Region(0, markdown_view.size())
         markdown = markdown_view.substr(total_region)
 

live-testing/images.md

@@ -1,5 +1,7 @@
 I'm not sure that it **actually** going to work, but it seems nicer than the [previous version][prev]
 
+this is a test, hello world
+
 This is the first image from the local file system (absolute path, sorry, it's not going
 to work on your system unless your username is math2001):
 

live-testing/test.md

@@ -13,6 +13,4 @@ if input("answer yes") != 'yes':
 
 this flickering is really annoying...
 
-this
-
 It looks like it's gone... Oh wait nah, it's still here...

resources/stylesheet.css

@@ -5,6 +5,7 @@ html {
 
 body {
     font-family: "Ubuntu", "DejaVu Sans", "Open Sans", sans-serif;
+    font-size: 15px;
 }
 
 blockquote {