Index: lib/redmine/helpers/gantt.rb
===================================================================
--- lib/redmine/helpers/gantt.rb	(revision 4732)
+++ lib/redmine/helpers/gantt.rb	(working copy)
@@ -98,17 +98,19 @@
         common_params.merge({:year => (date_from >> months).year, :month => (date_from >> months).month, :zoom => zoom, :months => months })
       end
 
-            ### Extracted from the HTML view/helpers
+      # Returns the list of projects to render
+      def project_list
+        projects = @project ? [@project] : Project.roots.visible.has_module('issue_tracking')
+        @query && @query.has_filter?('project_id') ? projects & Project.find(@query.values_for('project_id')) : projects
+      end
+
+      ### Extracted from the HTML view/helpers
       # Returns the number of rows that will be rendered on the Gantt chart
       def number_of_rows
         return @number_of_rows if @number_of_rows
         
-        rows = if @project
-          number_of_rows_on_project(@project)
-        else
-          Project.roots.visible.has_module('issue_tracking').inject(0) do |total, project|
-            total += number_of_rows_on_project(project)
-          end
+        rows = project_list().each do |total, project|
+          total += number_of_rows_on_project(project)
         end
         
         rows > @max_rows ? @max_rows : rows
@@ -161,16 +163,12 @@
         @subjects = '' unless options[:only] == :lines
         @lines = '' unless options[:only] == :subjects
         @number_of_rows = 0
-        
-        if @project
-          render_project(@project, options)
-        else
-          Project.roots.visible.has_module('issue_tracking').each do |project|
-            render_project(project, options)
-            break if abort?
-          end
+
+        project_list().each do |project|
+          render_project(project, options)
+          break if abort?
         end
-        
+
         @subjects_rendered = true unless options[:only] == :lines
         @lines_rendered = true unless options[:only] == :subjects
         
@@ -373,7 +371,7 @@
         output
       end
 
-      def line_for_issue(issue, options)
+      def line_for_issue(issue, options)  
         # Skip issues that don't have a due_before (due_date or version's due_date)
         if issue.is_a?(Issue) && issue.due_before
           coords = coordinates(issue.start_date, issue.due_before, issue.done_ratio, options[:zoom])