Redmine/app/views/projects/gantt.rhtml

<div class="contextual">
<%= l(:label_export_to) %>
<%= link_to 'PDF', {:zoom => @zoom, :year => @year_from, :month => @month_from, :months => @months, :tracker_ids => @selected_tracker_ids, :with_subprojects => params[:with_subprojects], :output => 'pdf'}, :class => 'icon icon-pdf' %>
</div>

<h2><%= l(:label_gantt) %></h2>

<% form_tag do %>
<table width="100%">
<tr>
<td align="left">
    <input type="text" name="months" size="2" value="<%= @months %>" />
    <%= l(:label_months_from) %>
    <%= select_month(@month_from, :prefix => "month", :discard_type => true) %>
    <%= select_year(@year_from, :prefix => "year", :discard_type => true) %>
    <%= hidden_field_tag 'zoom', @zoom %>
    <%= submit_tag l(:button_submit), :class => "button-small" %>    
</td>
<td>
    <a href="#" onclick="Element.toggle('trackerselect')"><%= l(:label_options) %></a>
    <div id="trackerselect" class="rightbox overlay" style="width:140px; display: none;">
    <p><strong><%=l(:label_tracker_plural)%></strong></p>
    <% @trackers.each do |tracker| %>
      <%= check_box_tag "tracker_ids[]", tracker.id, (@selected_tracker_ids.include? tracker.id.to_s) %>
      <%= tracker.name %><br />
    <% end %>
    <% if @project.children.any? %>
    <p><strong><%=l(:label_subproject_plural)%></strong></p>
    <%= check_box_tag "with_subprojects", 1, params[:with_subprojects] %> <%= l(:general_text_Yes) %>
    <% end %>
    <p><center><%= submit_tag l(:button_apply), :class => 'button-small' %></center></p>
    </div>
</td>
<td align="right">
<%= if @zoom < 4
    link_to image_tag('zoom_in.png'), {:zoom => (@zoom+1), :year => @year_from, :month => @month_from, :months => @months, :tracker_ids => @selected_tracker_ids, :with_subprojects => params[:with_subprojects]}
  else
    image_tag 'zoom_in_g.png'
  end %>
<%= if @zoom > 1
    link_to image_tag('zoom_out.png'),{:zoom => (@zoom-1), :year => @year_from, :month => @month_from, :months => @months, :tracker_ids => @selected_tracker_ids, :with_subprojects => params[:with_subprojects]}
  else
    image_tag 'zoom_out_g.png'
  end %>
</td>
</tr>
</table>
<% end %>

<% zoom = 1
@zoom.times { zoom = zoom * 2 }

subject_width = 260
header_heigth = 18

headers_height = header_heigth
show_weeks = false
show_days = false

if @zoom >1
    show_weeks = true
    headers_height = 2*header_heigth
    if @zoom > 2
        show_days = true
        headers_height = 3*header_heigth
    end
end

g_width = (@date_to - @date_from + 1)*zoom
g_height = [(20 * @issues.length + 6)+150, 206].max
t_height = g_height + headers_height
%>

<table width="100%" style="border:0; border-collapse: collapse;">
<tr>
<td style="width:260px;">

<div style="position:relative;height:<%= t_height + 24 %>px;width:<%= subject_width + 1 %>px;">
<div style="right:-2px;width:<%= subject_width %>px;height:<%= headers_height %>px;background: #eee;" class="gantt_hdr"></div>
<div style="right:-2px;width:<%= subject_width %>px;height:<%= t_height %>px;border-left: 1px solid #c0c0c0;overflow:hidden;" class="gantt_hdr"></div>
<%
#
# Tasks subjects
#
top = headers_height + 8
@issues.each do |i| %>
    <div style="position: absolute;line-height:1.2em;height:16px;top:<%= top %>px;left:4px;overflow:hidden;">
  	<small><%= link_to "#{i.tracker.name} ##{i.id}", { :controller => 'issues', :action => 'show', :id => i }, :title => "#{i.subject}" %>:
  	<%=h i.subject.sub(/^(.{30}[^\s]*\s).*$/, '\1 (...)') %></small>
  	</div>
    <% top = top + 20
end %>
</div>
</td>
<td>

<div style="position:relative;height:<%= t_height + 24 %>px;overflow:auto;">
<div style="width:<%= g_width-1 %>px;height:<%= headers_height %>px;background: #eee;" class="gantt_hdr">&nbsp;</div>
<% 
#
# Months headers
#
month_f = @date_from
left = 0
height = (show_weeks ? header_heigth : header_heigth + g_height)
@months.times do 
	width = ((month_f >> 1) - month_f) * zoom - 1
	%>
	<div style="left:<%= left %>px;width:<%= width %>px;height:<%= height %>px;" class="gantt_hdr">
	<%= link_to "#{month_f.year}-#{month_f.month}", { :year => month_f.year, :month => month_f.month, :zoom => @zoom, :months => @months, :tracker_ids => @selected_tracker_ids, :with_subprojects => params[:with_subprojects] }, :title => "#{month_name(month_f.month)} #{month_f.year}"%>
	</div>
	<% 
	left = left + width + 1
	month_f = month_f >> 1
end %>

<% 
#
# Weeks headers
#
if show_weeks
	left = 0
	height = (show_days ? header_heigth-1 : header_heigth-1 + g_height)
	if @date_from.cwday == 1
	    # @date_from is monday
        week_f = @date_from
	else
	    # find next monday after @date_from
		week_f = @date_from + (7 - @date_from.cwday + 1)
		width = (7 - @date_from.cwday + 1) * zoom-1
		%>
		<div style="left:<%= left %>px;top:19px;width:<%= width %>px;height:<%= height %>px;" class="gantt_hdr">&nbsp;</div>
		<% 
		left = left + width+1
	end %>
	<%
	while week_f <= @date_to
		width = (week_f + 6 <= @date_to) ? 7 * zoom -1 : (@date_to - week_f + 1) * zoom-1
		%>
		<div style="left:<%= left %>px;top:19px;width:<%= width %>px;height:<%= height %>px;" class="gantt_hdr">
		<small><%= week_f.cweek if width >= 16 %></small>
		</div>
		<% 
		left = left + width+1
		week_f = week_f+7
	end
end %>

<% 
#
# Days headers
#
if show_days
	left = 0
	height = g_height + header_heigth - 1
	wday = @date_from.cwday
	(@date_to - @date_from + 1).to_i.times do 
	width =  zoom - 1
	%>
	<div style="left:<%= left %>px;top:37px;width:<%= width %>px;height:<%= height %>px;font-size:0.7em;<%= "background:#f1f1f1;" if wday > 5 %>" class="gantt_hdr">
	<%= day_name(wday)[0,1] %>
	</div>
	<% 
	left = left + width+1
	wday = wday + 1
	wday = 1 if wday > 7
	end
end %>

<%
#
# Today red line
#
if Date.today >= @date_from and Date.today <= @date_to %>
    <div style="position: absolute;height:<%= g_height %>px;top:<%= headers_height + 1 %>px;left:<%= ((Date.today-@date_from+1)*zoom).floor()-1 %>px;width:10px;border-left: 1px dashed red;">&nbsp;</div>
<% end %>

<%
#
# Tasks
#
top = headers_height + 10
@issues.each do |i| %>
	<%
	i_start_date = (i.start_date >= @date_from ? i.start_date : @date_from )
	i_end_date = (i.due_date <= @date_to ? i.due_date : @date_to )
	
	i_done_date = i.start_date + ((i.due_date - i.start_date+1)*i.done_ratio/100).floor
	i_done_date = (i_done_date <= @date_from ? @date_from : i_done_date )
	i_done_date = (i_done_date >= @date_to ? @date_to : i_done_date )
	
	i_late_date = [i_end_date, Date.today].min if i_start_date < Date.today
	
	i_left = ((i_start_date - @date_from)*zoom).floor 	
	i_width = ((i_end_date - i_start_date + 1)*zoom).floor - 2                  # total width of the issue (- 2 for left and right borders)
	d_width = ((i_done_date - i_start_date)*zoom).floor - 2                     # done width
	l_width = i_late_date ? ((i_late_date - i_start_date+1)*zoom).floor - 2 : 0 # delay width
	%>
	<div style="top:<%= top %>px;left:<%= i_left %>px;width:<%= i_width %>px;" class="task task_todo">&nbsp;</div>
	<% if l_width > 0 %>
	    <div style="top:<%= top %>px;left:<%= i_left %>px;width:<%= l_width %>px;" class="task task_late">&nbsp;</div>
	<% end %>
	<% if d_width > 0 %>
	    <div style="top:<%= top %>px;left:<%= i_left %>px;width:<%= d_width %>px;" class="task task_done">&nbsp;</div>
	<% end %>
	<div style="top:<%= top %>px;left:<%= i_left + i_width + 5 %>px;background:#fff;" class="task">
	<%= i.status.name %>
	<%= (i.done_ratio).to_i %>%
	</div>
	<% # === tooltip === %>
	<div class="tooltip" style="position: absolute;top:<%= top %>px;left:<%= i_left %>px;width:<%= i_width %>px;height:12px;">
	<span class="tip">
    <%= render :partial => "issues/tooltip", :locals => { :issue => i }%>
	</span></div>
	<% top = top + 20
end %>
</div>
</td>
</tr>
</table>

<table width="100%">
<tr>
<td align="left"><%= link_to ('&#171; ' + l(:label_previous)), :year => (@date_from << @months).year, :month => (@date_from << @months).month, :zoom => @zoom, :months => @months, :tracker_ids => @selected_tracker_ids, :with_subprojects => params[:with_subprojects] %></td>
<td align="right"><%= link_to (l(:label_next) + ' &#187;'), :year => (@date_from >> @months).year, :month => (@date_from >> @months).month, :zoom => @zoom, :months => @months, :tracker_ids => @selected_tracker_ids, :with_subprojects => params[:with_subprojects] %></td>
</tr>
</table>