void CalculateScale(PrintAttributes newAttributes)
{
int dpi = Math.Max(newAttributes.GetResolution().HorizontalDpi, newAttributes.GetResolution().VerticalDpi);
int leftMargin = (int)(dpi * (float)newAttributes.MinMargins.LeftMils / 1000);
int rightMargin = (int)(dpi * (float)newAttributes.MinMargins.RightMils / 1000);
int topMargin = (int)(dpi * (float)newAttributes.MinMargins.TopMils / 1000);
int bottomMargin = (int)(dpi * (float)newAttributes.MinMargins.BottomMils / 1000);
int w = (int)(dpi * (float)newAttributes.GetMediaSize().WidthMils / 1000) - leftMargin - rightMargin;
int h = (int)(dpi * (float)newAttributes.GetMediaSize().HeightMils / 1000) - topMargin - bottomMargin;
scale = Math.Min((float)document.PageContentRect.Width() / w, (float)document.PageContentRect.Height() / h);
}
public override void OnLayout(PrintAttributes oldAttributes, PrintAttributes newAttributes,
CancellationSignal cancellationSignal, LayoutResultCallback callback, Bundle extras)
{
// If we are already cancelled, don't do any work.
if (cancellationSignal.IsCanceled)
{
callback.OnLayoutCancelled();
return;
}
// Now we determined if the print attributes changed in a way that
// would change the layout and if so we will do a layout pass.
bool layoutNeeded = false;
int density = System.Math.Max(newAttributes.GetResolution().HorizontalDpi,
newAttributes.GetResolution().VerticalDpi);
// Note that we are using the PrintedPdfDocument class which creates
// a PDF generating canvas whose size is in points (1/72") not screen
// pixels. Hence, this canvas is pretty small compared to the screen.
// The recommended way is to layout the content in the desired size,
// in this case as large as the printer can do, and set a translation
// to the PDF canvas to shrink in. Note that PDF is a vector format
// and you will not lose data during the transformation.
// The content width is equal to the page width minus the margins times
// the horizontal printer density. This way we get the maximal number
// of pixels the printer can put horizontally.
int marginLeft = (int)(density * (float)newAttributes.MinMargins.LeftMils / MILS_IN_INCH);
int marginRight = (int)(density * (float)newAttributes.MinMargins.RightMils / MILS_IN_INCH);
int contentWidth = (int)(density * (float)newAttributes.GetMediaSize()
.WidthMils / MILS_IN_INCH) - marginLeft - marginRight;
if (mRenderPageWidth != contentWidth)
{
mRenderPageWidth = contentWidth;
layoutNeeded = true;
}
// The content height is equal to the page height minus the margins times
// the vertical printer resolution. This way we get the maximal number
// of pixels the printer can put vertically.
int marginTop = (int)(density * (float)newAttributes.MinMargins.TopMils / MILS_IN_INCH);
int marginBottom = (int)(density * (float)newAttributes.MinMargins.BottomMils / MILS_IN_INCH);
int contentHeight = (int)(density * (float)newAttributes.GetMediaSize()
.HeightMils / MILS_IN_INCH) - marginTop - marginBottom;
if (mRenderPageHeight != contentHeight)
{
mRenderPageHeight = contentHeight;
layoutNeeded = true;
}
// Create a context for resources at printer density. We will
// be inflating views to render them and would like them to use
// resources for a density the printer supports.
if (mPrintContext == null || mPrintContext.Resources.Configuration.DensityDpi != density)
{
var configuration = new Configuration();
configuration.DensityDpi = density;
mPrintContext = pcc.CreateConfigurationContext(configuration);
mPrintContext.SetTheme(Android.Resource.Style.ThemeHoloLight);
}
// If no layout is needed that we did a layout at least once and
// the document info is not null, also the second argument is false
// to notify the system that the content did not change. This is
// important as if the system has some pages and the content didn't
// change the system will ask, the application to write them again.
if (!layoutNeeded)
{
callback.OnLayoutFinished(mDocumentInfo, false);
return;
}
// For demonstration purposes we will do the layout off the main
// thread but for small content sizes like this one it is OK to do
// that on the main thread.
var asyncTask = new MyOnLayoutAsyncTask(this, newAttributes, cancellationSignal, callback);
asyncTask.ExecuteOnExecutor(AsyncTask.ThreadPoolExecutor, (Java.Lang.Void[])null);
}