Monday, May 12, 2008

Scrolling, without using ScrollViewer!

The main objective when building SimpleViewer-SL was to keep the executable as small as possible and hence I didn't have the option of using ScrollViewer. I still needed scrolling functionality though and hence had to take some alternate approach. This post is a result of my findings. There is possibly no reason for anyone to take this approach, unless there is a compelling reason to not use ScrollViewer, but it might prove useful!

So how did I go about implementing scrolling? The trick is to contain the visible area and use TranslateTransform.

Let's look at the Xaml first
<UserControl x:Class="SimpleViewer_SL.Thumbnails"
<Grid x:Name="LayoutRoot" HorizontalAlignment="Center" VerticalAlignment="Center">
<Grid x:Name="LayoutThumbnailsViewport" HorizontalAlignment="Left">
<Grid x:Name="LayoutThumbnails" HorizontalAlignment="Left">
<TranslateTransform x:Name="GridTranslate" />
<Storyboard x:Name="GridScrollStoryboard">
<DoubleAnimation x:Name="GridScrollAnimation" Storyboard.TargetName="GridTranslate" Storyboard.TargetProperty="X" Duration="00:00:00.5"/>
<Canvas x:Name="RightNav" Height="25" Width="30" Background="Transparent" HorizontalAlignment="Right">
<Path Height="25" Width="30" Stretch="Fill"
Data="F1 M 0,50L 130,50L 80,0L 130,0L 200,70L 130,140L 80,140L 130,90L 0,90L 0,50 Z">
<Canvas x:Name="LeftNav" Height="25" Width="30" Background="Transparent" HorizontalAlignment="Left">
<Path Height="25" Width="30" Stretch="Fill"
Data="F1 M 200,90L 70,90L 120,140L 70,140L 0,70L 70,0L 120,0L 70,50L 200,50L 200,90 Z">

What we are trying to do here is display the thumbnails in a grid, but, as you can see from the above Xaml, I have had to create 3 grids to implement scrolling.
  • LayoutThumbnails - This is the grid which will host the thumbnails
  • LayoutThumbnailsViewport - This is the grid which will host the translated thumbnails
  • LayoutRoot - This is the grid which will host the clipped thumbnails
  • GridTranslate - This exposes the translate transform of LayoutThumbnails
  • GridScrollStoryboard - This is the storyboard that animates GridTranslate to simulate (horizontal) scrolling
Now for some code
public partial class Thumbnails : UserControl
Page _parent = null;
int _borderWidth = 2;
int _selectedThumbnailIndex = -1;
int _rowCount = 0;
int _colCount = 0;
int _totalColCount = 0;
int _numPages = 0;
int _currPage = 0;
Size _thumbSize = new Size { Width = 65, Height = 65 };
int _borderPlusPaddingWidth = 0;

public double ControlWidth { get { return (_thumbSize.Width + (_borderPlusPaddingWidth * 2)) * _colCount; }}

public Thumbnails(Page parent)
_parent = parent;
_rowCount = _parent.Settings.ThumbnailRows;
_colCount = _parent.Settings.ThumbnailColumns;
_totalColCount = (int)(Math.Ceiling((double)_parent.Settings.ImagesSettings.Count / _rowCount));
_numPages = (int)(Math.Ceiling((double)_totalColCount / _colCount));
_borderPlusPaddingWidth = _parent.Settings.ThumbPadding + _borderWidth;


LayoutRoot.Width = ControlWidth; // ****1****
LayoutThumbnailsViewport.Width = ControlWidth * _numPages; // ****2****


int CreateLayout() {
// Thumbnails
LayoutRoot.RowDefinitions.Add(new RowDefinition());
LayoutThumbnailsViewport.SetValue(Grid.RowProperty, 0);

if (_numPages > 0) {
// Navigation Arrows
LayoutRoot.RowDefinitions.Add(new RowDefinition { Height = new GridLength(30) });
RightNav.SetValue(Grid.RowProperty, 1);
LeftNav.SetValue(Grid.RowProperty, 1);

void DrawThumbnails()
for (int row = 0; row < _rowCount; row++) {
LayoutThumbnails.RowDefinitions.Add(new RowDefinition { Height = new GridLength(_thumbSize.Height + (_borderPlusPaddingWidth * 2)) });

for (int col = 0; col < _colCount * _numPages; col++) {
LayoutThumbnails.ColumnDefinitions.Add(new ColumnDefinition { Width = new GridLength(_thumbSize.Width + (_borderPlusPaddingWidth * 2)) });

int imageIndex = 0;
int startCol = 0;
for (int page = 0; page < _numPages; page++) {
for (int row = 0; row < _rowCount; row++) {
for (int col = 0; col < _colCount && imageIndex < _parent.Settings.ImagesSettings.Count; col++) {
CreateImage(row, col + startCol, imageIndex);
startCol += _colCount;

LeftNav.MouseLeftButtonUp += (sender, e) => {

RightNav.MouseLeftButtonUp += (sender, e) => {

public void CreateImage(int row, int col, int imageIndex)
Image thumb = new Image();
thumb.Source = new BitmapImage(new Uri(_parent.Settings.ThumbPath + _parent.Settings.ImagesSettings[imageIndex].Name, UriKind.Relative));

Border border = new Border {
Width = _thumbSize.Width + (_borderWidth*2),
Height = _thumbSize.Height + (_borderWidth*2),
BorderThickness = new Thickness(_borderWidth),
BorderBrush = new SolidColorBrush(_parent.Settings.FrameColor),
Margin = new Thickness(_parent.Settings.ThumbPadding),
Opacity = 0.6
border.SetValue(Grid.RowProperty, row);
border.SetValue(Grid.ColumnProperty, col);
border.SetValue(NameProperty, "Image" + imageIndex.ToString());
border.Tag = imageIndex.ToString(); // Tag can only handle Strings as of SL2 B1 release

border.Child = thumb;

border.MouseLeftButtonUp += (sender, e) => {
Rect LayoutRootRect = new Rect(0, 0, LayoutRoot.RenderSize.Width, LayoutRoot.RenderSize.Height);
if (LayoutRootRect.Contains(e.GetPosition(LayoutRoot))) { // ****3****
Border currentBorder = (Border)sender;
SelectedThumbnailIndex = Int32.Parse((string)currentBorder.Tag);

bool CanScrollRight { get { return ((_currPage + 1) < _numPages); }}
bool CanScrollLeft { get { return (_currPage > 0); }}

void ScrollRight()
if (CanScrollRight) {
GridScrollAnimation.To = -(_thumbSize.Width + (_borderPlusPaddingWidth * 2)) * _colCount * _currPage;

void ScrollLeft()
if (CanScrollLeft) {
GridScrollAnimation.To = -(_thumbSize.Width + (_borderPlusPaddingWidth * 2)) * _colCount * _currPage;

Most of the code is self explanatory but I would like to elaborate on a few key points which is highlighted in the code:
  1. The width of LayoutThumbnailsViewport should be equal to or greater than the width of the entire grid. If the width is not explicitly set or is less than the width of the entire grid, translatetransform will clip the contents that lie outside the area of the grid
  2. The width of LayoutRoot should be set to the viewing area. This should be less than the width of LayoutThumbnailsViewport if scrolling is desired
  3. One undesired effect of creating this layout is that the underlying grid (LayoutThumbnails) and hence the thumbnails receive mouse events even for the contents that is outside the visible area (LayoutRoot). To circumvent this I had to put this check - if (LayoutRootRect.Contains(e.GetPosition(LayoutRoot))) - in the border.MouseLeftButtonUp event handler. (Note that border is synonymous with thumbnail)

Sunday, May 4, 2008

SimpleViewer-SL Beta 1

Update 5/8/08: Fixed blank screen bug when navigating between thumbnails, and improved browser resizing support...

The Silverlight version of the flash based photo album viewer - SimpleViewer, is here! I decided to call it SimpleViewer-SL for now.

Here are a few examples that were created using SimpleViewer-SL (the keyboard arrow keys are supported as well)
  1. Thumbnails on the left, 3x3 grid

  2. Thumbnails on the right, 5x4 grid

  3. Thumbnails on bottom, 2x4 grid

  4. Thumbnails on the left, with background image

SimpleViewer-SL is highly customizable. It is compatible with SimpleViewer and hence all options exposed by SimpleViewer are applicable to SimpleViewer-SL as well. The options are listed here. The only XML option that is not supported at this time is enableRightClickOpen. Note that the text fields like title and Caption should be plain text (no HTML) for now since I haven't implemented the HTML text control as yet. As for the HTML options, the only supported option is xmlDataPath. The HTML option should be passed to the SimpleViewer-SL Silverlight object using the param tag - <param name="initParams" value="xmlDataPath=gallery1.xml" />

The album can be created using any of the methods described here . After creating the albums, a few modifications to the generated file(s) is required to make it work on SimpleViewer-SL.

The xap can be found here.

The directory structure for the samples is as follows:

65x65 thumbnail images
the corresponding big images

Between the above links, the sample html and xml files, it should be fairly straightforward for anyone to figure out how to use SimpleViewer-SL. Overall it is fairly feature complete but there is always room for improvement. It is a little unstable, in that sometime navigating between thumbnails results in a blank screen, but I think it is more to do with Silverlight being a Beta release (looks like it was more to do with my code!).

This exercise took me a little over a week of part time work so I have to say that I am pretty impressed with Silverlight. Most of my time was spent in figuring out a way to work around Silverlight 2 Beta 1 bugs. I suspect that I can simplify the code a bit after the final release of Siverlight 2. Nevertheless, the current size of SimpleViewer-SL is a mere 17kb, the same as SimpleViewer, with lots of opportunity for improvement.

For those looking for the code, I am planning to codeplex it when I get some time. Feel free to leave comments to pressure me into doing it sooner rather than later!

Deep Zoom Composer Updated!

A nice update to Deep Zoom Composer can be found here -

The new update includes: improved exporting (includes mousewheel, pan, zoom, and keyboard functionality), better design experience, collection export bug fix, and greater access to help.