Merge pull request #4511 from nyalldawson/composer_async

Asyncronously render composer map previews

Author: nyalldawson

doc/api_break.dox

@@ -640,6 +640,9 @@ and setAtlasScalingMode() instead.
 - setMapCanvas() was removed. This is no longer required to draw map annotations, which are instead retrieved from the composition's
 associated project's annotationManager()
 - setDrawCanvasItems() and drawCanvasItems() were renamed to setDrawAnnotations() and drawAnnotations()
+- setCacheUpdated(), updateCachedImage(), renderModeUpdateCachedImage() and cache() were removed. Use invalidateCache() instead.
+- The PreviewMode mode enums were removed. These are no longer used.
+- previewMode() and setPreviewMode() were removed. These are no longer required.
 
 
 QgsComposerMapGrid        {#qgis_api_break_3_0_QgsComposerMapGrid}

python/auto_sip.blacklist

@@ -121,7 +121,6 @@ core/composer/qgscomposeritemcommand.sip
 core/composer/qgscomposeritemgroup.sip
 core/composer/qgscomposerlabel.sip
 core/composer/qgscomposerlegend.sip
-core/composer/qgscomposermap.sip
 core/composer/qgscomposermapgrid.sip
 core/composer/qgscomposermapitem.sip
 core/composer/qgscomposermapoverview.sip