Fix text rendering when Inkscape multi-line text has an empty first line.

Possible fix for GitLab issue #45.

3 files changed, 85 insertions, 7 deletions

diff --git a/src/libnrtype/Layout-TNG-Compute.cpp b/src/libnrtype/Layout-TNG-Compute.cpp
index a248847f7..f31fffa86 100644
--- a/src/libnrtype/Layout-TNG-Compute.cpp
+++ b/src/libnrtype/Layout-TNG-Compute.cpp
@@ -560,6 +560,8 @@ void Layout::Calculator::_outputLine(ParagraphInfo const &para,
         new_line.baseline_y += line_height.getTypoAscent();
     }
 
+    TRACE(("    initial new_line.baseline_y: %f\n", new_line.baseline_y ));
+
     new_line.in_shape = _current_shape_index;
     _flow._lines.push_back(new_line);
 
@@ -603,12 +605,15 @@ void Layout::Calculator::_outputLine(ParagraphInfo const &para,
                 // NOTE: for vertical text, "y" is the user-space "x" value.
                 if( it_chunk->broken_spans.front().start.iter_span->y._set ) {
 
-                    // Use set "y" attribute
+                    // Use set "y" attribute for baseline
                     new_line.baseline_y = it_chunk->broken_spans.front().start.iter_span->y.computed;
 
+                    TRACE(("      chunk new_line.baseline_y: %f\n", new_line.baseline_y ));
+
                     // Save baseline
                     _flow._lines.back().baseline_y = new_line.baseline_y;
 
+                    // Calculate new top of box... given specified baseline.
                     double top_of_line_box = new_line.baseline_y;
                     if( _block_progression == RIGHT_TO_LEFT ) {
                         // Vertical text, use em box center as baseline
@@ -620,7 +625,7 @@ void Layout::Calculator::_outputLine(ParagraphInfo const &para,
                         top_of_line_box -= line_height.getTypoAscent();
                     }
                     TRACE(("      y attribute set, next line top_of_line_box: %f\n", top_of_line_box ));
-                    // Set the initial y coordinate of the next line (see above).
+                    // Set the initial y coordinate of the for this line (see above).
                     _scanline_maker->setNewYCoordinate(top_of_line_box);
                 }
 
@@ -952,10 +957,12 @@ void Layout::Calculator::_createFirstScanlineMaker()
     if (_flow._input_wrap_shapes.empty()) {
         // create the special no-wrapping infinite scanline maker
         double initial_x = 0, initial_y = 0;
-        if (!text_source->x.empty())
+        if (!text_source->x.empty()) {
             initial_x = text_source->x.front().computed;
-        if (!text_source->y.empty())
+        }
+        if (!text_source->y.empty()) {
             initial_y = text_source->y.front().computed;
+        }
         _scanline_maker = new InfiniteScanlineMaker(initial_x, initial_y, _block_progression);
         TRACE(("  wrapping disabled\n"));
     }
@@ -1878,6 +1885,33 @@ bool Layout::Calculator::calculate()
                 keep_going = false;
                 break;   // No room for text and not useful to try again at same place.
             }
+
+            // For Inkscape multi-line text (using role="line") we run into a problem if the first
+            // line is empty - namely, there is no character to attach a 'y' attribute value. The
+            // result is that the code that takes a baseline position (e.g. 'y') and finds the top
+            // of the layout box is bypassed resulting in wrongly placed text (we layout the text
+            // relative to the top of the box as this is required for text-in-a-shape). We don't
+            // know how to find the top of the box from the 'y' position until we have found the
+            // line height parameters for the given line (after calling _findChunksForLine() just
+            // above).
+            if (para.first_input_index == 0) {
+
+                // Calculate new top of box... given specified baseline.
+                double top_of_line_box = _scanline_maker->yCoordinate(); // Set in constructor.
+                if( _block_progression == RIGHT_TO_LEFT ) {
+                    // Vertical text, use em box center as baseline
+                    top_of_line_box += 0.5 * line_box_height.emSize();
+                } else if (_block_progression == LEFT_TO_RIGHT ) {
+                    // Vertical text, use em box center as baseline
+                    top_of_line_box -= 0.5 * line_box_height.emSize();
+                } else {
+                    top_of_line_box -= line_box_height.getTypoAscent();
+                }
+                TRACE(("      y attribute set, next line top_of_line_box: %f\n", top_of_line_box ));
+                // Set the initial y coordinate of the for this line (see above).
+                _scanline_maker->setNewYCoordinate(top_of_line_box);
+            }
+
             _outputLine(para, line_box_height, line_chunk_info);
             _scanline_maker->setLineHeight( line_box_height );
             _scanline_maker->completeLine(); // Increments y by line height
diff --git a/src/object/sp-text.cpp b/src/object/sp-text.cpp
index ff8bd9af7..b65170642 100644
--- a/src/object/sp-text.cpp
+++ b/src/object/sp-text.cpp
@@ -617,7 +617,7 @@ unsigned SPText::_buildLayoutInput(SPObject *object, Inkscape::Text::Layout::Opt
             // we've found 'x' and 'y' and then creating the Shape at the end.)
             if (is_horizontal()) {
                 // Horizontal text
-                SVGLength* y = attributes.getFirstYLength();
+                SVGLength* y = _getFirstYLength();
                 if (y) {
                     optional_attrs.y.push_back(*y);
                 } else {
@@ -625,14 +625,13 @@ unsigned SPText::_buildLayoutInput(SPObject *object, Inkscape::Text::Layout::Opt
                 }
             } else {
                 // Vertical text
-                SVGLength* x = attributes.getFirstXLength();
+                SVGLength* x = _getFirstXLength();
                 if (x) {
                     optional_attrs.x.push_back(*x);
                 } else {
                     std::cerr << "SPText::_buildLayoutInput: No 'x' attribute value with vertical 'inline-size'!" << std::endl;
                 }
             }
-
         }
 
         // set textLength on the entire layout, see note in TNG-Layout.h
@@ -773,6 +772,47 @@ Shape* SPText::_buildExclusionShape() const
     return result;
 }
 
+
+// SVG requires one to use the first x/y value found on a child element if x/y not given on text
+// element. TODO: Recurse.
+SVGLength*
+SPText::_getFirstXLength()
+{
+    SVGLength* x = attributes.getFirstXLength();
+
+    if (!x) {
+        for (auto& child: children) {
+            if (SP_IS_TSPAN(&child)) {
+                SPTSpan *tspan = SP_TSPAN(&child);
+                x = tspan->attributes.getFirstXLength();
+                break;
+            }
+        }
+    }
+
+    return x;
+}
+
+
+SVGLength*
+SPText::_getFirstYLength()
+{
+    SVGLength* y = attributes.getFirstYLength();
+
+    if (!y) {
+        for (auto& child: children) {
+            if (SP_IS_TSPAN(&child)) {
+                SPTSpan *tspan = SP_TSPAN(&child);
+                y = tspan->attributes.getFirstYLength();
+                break;
+            }
+        }
+    }
+
+    return y;
+}
+
+
 void SPText::rebuildLayout()
 {
     layout.clear();
diff --git a/src/object/sp-text.h b/src/object/sp-text.h
index a4c8b9d84..f2483bd03 100644
--- a/src/object/sp-text.h
+++ b/src/object/sp-text.h
@@ -78,6 +78,10 @@ private:
     /** Union all exlusion shapes. */
     Shape* _buildExclusionShape() const;
 
+    /** Find first x/y valuse which may be in a descendent element. */
+    SVGLength* _getFirstXLength();
+    SVGLength* _getFirstYLength();
+
 public:
     /** Optimize textpath text on next set_transform. */
     void optimizeTextpathText() {_optimizeTextpathText = true;}