Improve render script performance

The script no longer creates a new inkscape process for every
png export. Instead a single inkscape process is created for each
svg-file and export commands are simply fed to it. This allows for
using multiple CPU-cores and avoids the cost of constantly starting
up inkscape.

The script no longer renders out the entire icon set each time it's
run, instead it updates only icons which have been changed since
the last time the script finished running. This also means if the
script is interrupted while rendering, any svg-files what was
finished will not render out again saving time.

.gitignore

@@ -9,3 +9,4 @@ configure
 install-sh
 missing
 *.tmp
+*_timestamp

src/render_icons.sh

@@ -1,7 +1,6 @@
 #!/bin/bash
 
 INKSCAPE="/usr/bin/inkscape"
-OPTIPNG="/usr/bin/optipng"
 
 pushd `dirname $0` > /dev/null
 DIR="$( cd "$(dirname "$0")" ; pwd -P )"
@@ -9,62 +8,73 @@ popd > /dev/null
 
 cd ${DIR}
 
+TYPES=(actions apps categories devices emblems mimetypes places status)
+SIZES=(16 22 24 32 48 64 96 128)
+
 THEMEDIR=../Arc
 
-mkdir -p $THEMEDIR
+# Set up all the folders in the theme directory.
+mkdir -p $THEMEDIR/{actions,apps,categories,devices,emblems,mimetypes,places,status}/{16,22,24,32,48,64,96,128}{,@2x}
+
+cp -u index.theme $THEMEDIR/index.theme
 
-for CONTEXT in actions apps categories devices emblems mimetypes places status
+for CONTEXT in ${TYPES[@]}
 do
+    for SIZE in ${SIZES[@]}
+    do
+        cp -ru $CONTEXT/symlinks/* $THEMEDIR/$CONTEXT/$SIZE
+        cp -ru $CONTEXT/symlinks/* $THEMEDIR/$CONTEXT/$SIZE@2x
+        cp -ru $CONTEXT/symbolic $THEMEDIR/$CONTEXT
+    done
+done
 
-    mkdir -p $THEMEDIR/$CONTEXT
-    mkdir -p $THEMEDIR/$CONTEXT
+rm -rf $THEMEDIR/actions/{32,32@2x,48,48@2x,64,64@2x,96,96@2x,128,128@2x} # derp
 
-    cp -r $CONTEXT/symbolic $THEMEDIR/$CONTEXT
+# TODO
+cp -ru animations $THEMEDIR/.
+cp -ru panel $THEMEDIR/.
 
-    for SIZE in 16 22 24 32 48 64 96 128
-    do
-        $INKSCAPE -S $CONTEXT.svg | grep -E "_$SIZE" | sed 's/\,.*$//' > index.tmp
 
-        mkdir -p $THEMEDIR/$CONTEXT/$SIZE
-        mkdir -p $THEMEDIR/$CONTEXT/$SIZE@2x
+# Generates inkscape export commands for the given
+# svg-file that can be piped to inkscape.
+genInkscapeCmds() {
 
-        cp -r $CONTEXT/symlinks/* $THEMEDIR/$CONTEXT/$SIZE
-        cp -r $CONTEXT/symlinks/* $THEMEDIR/$CONTEXT/$SIZE@2x
+    local CONTEXT=$1
 
-        for OBJECT_ID in `cat index.tmp`
+    for SIZE in ${SIZES[@]}
+    do
+        echo "Rendering icons $CONTEXT.svg @$SIZE" >&2
+        for OBJECT_ID in `cat <($INKSCAPE -S $CONTEXT.svg | grep -E "_$SIZE" | sed 's/\,.*$//')`
         do
-
-            ICON_NAME=$(sed "s/\_$SIZE.*$//" <<< $OBJECT_ID)
-
-            if [ -f $THEMEDIR/$CONTEXT/$SIZE/$ICON_NAME.png ]; then
-                echo $THEMEDIR/$CONTEXT/$SIZE/$ICON_NAME.png exists.
-            else
-                echo
-                echo Rendering $THEMEDIR/$CONTEXT/$SIZE/$ICON_NAME.png
-                $INKSCAPE --export-id=$OBJECT_ID \
-                          --export-id-only \
-                          --export-png=$THEMEDIR/$CONTEXT/$SIZE/$ICON_NAME.png $CONTEXT.svg >/dev/null \
-                && $OPTIPNG -o7 --quiet $ASSETS_DIR/$i.png 
-            fi
-            if [ -f $THEMEDIR/$CONTEXT/$SIZE@2x/$ICON_NAME.png ]; then
-                echo $THEMEDIR/$CONTEXT/$SIZE@2x/$ICON_NAME.png exists.
-            else
-                echo
-                echo Rendering $THEMEDIR/$CONTEXT/$SIZE@2x/$ICON_NAME.png
-                $INKSCAPE --export-id=$OBJECT_ID \
-                          --export-dpi=180 \
-                          --export-id-only \
-                          --export-png=$THEMEDIR/$CONTEXT/$SIZE@2x/$ICON_NAME.png $CONTEXT.svg >/dev/null \
-                && $OPTIPNG -o7 --quiet $ASSETS_DIR/$i@2.png 
-            fi
+            local ICON_NAME=$(sed "s/\_$SIZE.*$//" <<< $OBJECT_ID)
+
+            echo \
+                "--export-id=$OBJECT_ID" \
+                "--export-id-only" \
+                "--export-png=$THEMEDIR/$CONTEXT/$SIZE/$ICON_NAME.png $CONTEXT.svg"
+    
+            echo \
+                "--export-id=$OBJECT_ID" \
+                "--export-dpi=180" \
+                "--export-id-only" \
+                "--export-png=$THEMEDIR/$CONTEXT/$SIZE@2x/$ICON_NAME.png $CONTEXT.svg"
         done
     done
+}
+
+for CONTEXT in ${TYPES[@]}
+do
+    # Only render out the icons if the svg-file has been modified
+    # since we finished rendering it out last.
+    if [[ $CONTEXT.svg -nt .${CONTEXT}_timestamp ]]
+    then
+        genInkscapeCmds $CONTEXT | $INKSCAPE --shell > /dev/null && touch .${CONTEXT}_timestamp &
+    else
+        echo "No changes to $CONTEXT.svg, skipping..."
+    fi
 done
 
-rm index.tmp
-cp index.theme $THEMEDIR/index.theme
-rm -rf $THEMEDIR/actions/{32,32@2x,48,48@2x,64,64@2x,96,96@2x,128,128@2x} # derp
+wait
 
-# TODO
-cp -r animations $THEMEDIR/.
-cp -r panel $THEMEDIR/.
+# Remove all empty directories from the theme folder.
+find $THEMEDIR -type d -empty -delete