Doc: Add macro for embedding YouTube videos

This macro adds a \youtube <ID> command that embeds a YouTube link
into the documentation.

The video container scales to a specified percentage of the available
horizontal area. It assumes a source aspect ratio of 16:9, but looks
acceptable with other ratios.

For backends that do not support <iframe> (e.g. QTextBrowser), shows
a clickable video thumbnail that open the YouTube link in an external
browser window. Unfortunately, QTextBrowser cannot load images from
a remote URL, so we need to store a thumbnail image in the .qch file.

Change-Id: I3a3a0c5a20dd90e5cec6357ba70a23ee47dbe825
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>
Reviewed-by: Venugopal Shivashankar <Venugopal.Shivashankar@qt.io>

1 files changed, 19 insertions, 0 deletions

diff --git a/doc/global/template/style/online.css b/doc/global/template/style/online.css
index 3c305f3ddb..2d758f5301 100644
--- a/doc/global/template/style/online.css
+++ b/doc/global/template/style/online.css
@@ -1721,3 +1721,22 @@ a.qa-mark:target:before {
   color: #ff0000;
 }
 
+.mainContent .video {
+  width:60%;
+  max-width:640px;
+  margin: 0.5em 0 1.5em 0.5em;
+  position:relative;
+  display:table
+}
+
+.mainContent .video > .vspan {
+  padding-top:60%;
+  display:block
+}
+.mainContent .video iframe {
+  width:100%;
+  height:100%;
+  position:absolute;
+  top:0;
+  left:0
+}