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Fix calculation of atlas map extent when set to fixed scale mode

Credit to m-kuhn for discovering the fix
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nyalldawson committed Nov 24, 2014
1 parent 7ef5092 commit b106f8225324237175aac741ede9eb5d3268edcd
Showing with 14 additions and 13 deletions.
  1. +14 −13 src/core/composer/qgsatlascomposition.cpp
@@ -514,7 +514,8 @@ void QgsAtlasComposition::prepareMap( QgsComposerMap* map )
double ya1 = mTransformedFeatureBounds.yMinimum();
double ya2 = mTransformedFeatureBounds.yMaximum();
QgsRectangle newExtent = mTransformedFeatureBounds;
QgsRectangle mOrigExtent( map->extent() );
QgsRectangle originalExtent( map->extent() );
QgsRectangle currentExtent( *map->currentMapExtent() );

//sanity check - only allow fixed scale mode for point layers
bool isPointLayer = false;
@@ -536,19 +537,19 @@ void QgsAtlasComposition::prepareMap( QgsComposerMap* map )
QgsScaleCalculator calc;
calc.setMapUnits( composition()->mapSettings().mapUnits() );
calc.setDpi( 25.4 );
double originalScale = calc.calculate( mOrigExtent, map->rect().width() );
double originalScale = calc.calculate( currentExtent, map->rect().width() );
double geomCenterX = ( xa1 + xa2 ) / 2.0;
double geomCenterY = ( ya1 + ya2 ) / 2.0;

if ( map->atlasScalingMode() == QgsComposerMap::Fixed || isPointLayer )
{
// only translate, keep the original scale (i.e. width x height)
double xMin = geomCenterX - mOrigExtent.width() / 2.0;
double yMin = geomCenterY - mOrigExtent.height() / 2.0;
double xMin = geomCenterX - currentExtent.width() / 2.0;
double yMin = geomCenterY - currentExtent.height() / 2.0;
newExtent = QgsRectangle( xMin,
yMin,
xMin + mOrigExtent.width(),
yMin + mOrigExtent.height() );
xMin + currentExtent.width(),
yMin + currentExtent.height() );

//scale newExtent to match original scale of map
//this is required for geographic coordinate systems, where the scale varies by extent
@@ -558,14 +559,14 @@ void QgsAtlasComposition::prepareMap( QgsComposerMap* map )
else if ( map->atlasScalingMode() == QgsComposerMap::Predefined )
{
// choose one of the predefined scales
double newWidth = mOrigExtent.width();
double newHeight = mOrigExtent.height();
double newWidth = currentExtent.width();
double newHeight = currentExtent.height();
const QVector<qreal>& scales = mPredefinedScales;
for ( int i = 0; i < scales.size(); i++ )
{
double ratio = scales[i] / originalScale;
newWidth = mOrigExtent.width() * ratio;
newHeight = mOrigExtent.height() * ratio;
newWidth = currentExtent.width() * ratio;
newHeight = currentExtent.height() * ratio;

// compute new extent, centered on feature
double xMin = geomCenterX - newWidth / 2.0;
@@ -593,20 +594,20 @@ void QgsAtlasComposition::prepareMap( QgsComposerMap* map )
// auto scale

double geomRatio = mTransformedFeatureBounds.width() / mTransformedFeatureBounds.height();
double mapRatio = mOrigExtent.width() / mOrigExtent.height();
double mapRatio = originalExtent.width() / originalExtent.height();

// geometry height is too big
if ( geomRatio < mapRatio )
{
// extent the bbox's width
//extend the bbox's width
double adjWidth = ( mapRatio * mTransformedFeatureBounds.height() - mTransformedFeatureBounds.width() ) / 2.0;
xa1 -= adjWidth;
xa2 += adjWidth;
}
// geometry width is too big
else if ( geomRatio > mapRatio )
{
// extent the bbox's height
//extend the bbox's height
double adjHeight = ( mTransformedFeatureBounds.width() / mapRatio - mTransformedFeatureBounds.height() ) / 2.0;
ya1 -= adjHeight;
ya2 += adjHeight;

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