Allow calculating a nicer normal line-height

crengine/include/lvdocviewprops.h

@@ -90,6 +90,7 @@
 // use 0 for old crengine behaviour (no support for absolute units and 1css px = 1 screen px)
 #define PROP_RENDER_DPI                 "crengine.render.dpi"
 #define PROP_RENDER_SCALE_FONT_WITH_DPI "crengine.render.scale.font.with.dpi"
+#define PROP_RENDER_MIN_NORMAL_LINE_HEIGHT "crengine.render.min.normal.line.height"
 #define PROP_RENDER_BLOCK_RENDERING_FLAGS "crengine.render.block.rendering.flags"
 #define PROP_REQUESTED_DOM_VERSION      "crengine.render.requested_dom_version"
 

crengine/include/lvrend.h

@@ -188,8 +188,10 @@ bool getInkOffsets( ldomNode * node, lvRect &inkOffsets, bool measure_hidden_con
 #define BASE_CSS_DPI 96 // at 96 dpi, 1 css px = 1 screen px
 #define DEF_RENDER_DPI 96
 #define DEF_RENDER_SCALE_FONT_WITH_DPI 0
+#define DEF_RENDER_MIN_NORMAL_LINE_HEIGHT 0
 extern int gRenderDPI;
 extern bool gRenderScaleFontWithDPI;
+extern int gRenderMinNormalLineHeight;
 extern int gRootFontSize;
 
 #define INTERLINE_SCALE_FACTOR_NO_SCALE 1024

crengine/src/lvdocview.cpp

@@ -6721,6 +6721,7 @@ void LVDocView::propsUpdateDefaults(CRPropRef props) {
 
     props->setIntDef(PROP_RENDER_DPI, DEF_RENDER_DPI); // 96 dpi
     props->setIntDef(PROP_RENDER_SCALE_FONT_WITH_DPI, DEF_RENDER_SCALE_FONT_WITH_DPI); // no scale
+    props->setIntDef(PROP_RENDER_MIN_NORMAL_LINE_HEIGHT, DEF_RENDER_MIN_NORMAL_LINE_HEIGHT); // no scale
     props->setIntDef(PROP_RENDER_BLOCK_RENDERING_FLAGS, DEF_RENDER_BLOCK_RENDERING_FLAGS);
 
     props->setIntDef(PROP_FILE_PROPS_FONT_SIZE, 22);
@@ -7080,6 +7081,12 @@ CRPropRef LVDocView::propsApply(CRPropRef props) {
                 gRenderScaleFontWithDPI = value;
                 REQUEST_RENDER("propsApply render scale font with dpi")
             }
+        } else if (name == PROP_RENDER_MIN_NORMAL_LINE_HEIGHT) {
+            int value = props->getIntDef(PROP_RENDER_MIN_NORMAL_LINE_HEIGHT, DEF_RENDER_MIN_NORMAL_LINE_HEIGHT);
+            if ( gRenderMinNormalLineHeight != value ) {
+                gRenderMinNormalLineHeight = value;
+                REQUEST_RENDER("propsApply render min normal line height")
+            }
         } else if (name == PROP_FORMAT_SPACE_WIDTH_SCALE_PERCENT) {
             int value = props->getIntDef(PROP_FORMAT_SPACE_WIDTH_SCALE_PERCENT, DEF_SPACE_WIDTH_SCALE_PERCENT);
             if (m_doc) // not when noDefaultDocument=true

crengine/src/lvrend.cpp

@@ -52,6 +52,10 @@
 
 int gRenderDPI = DEF_RENDER_DPI; // if 0: old crengine behaviour: 1px/pt=1px, 1in/cm/pc...=0px
 bool gRenderScaleFontWithDPI = DEF_RENDER_SCALE_FONT_WITH_DPI;
+int gRenderMinNormalLineHeight = DEF_RENDER_MIN_NORMAL_LINE_HEIGHT;
+
+static const css_length_t relative_normal_line_height = css_length_t(css_val_em, 1*256 + (256 * 5 + 100 / 2) / 100); // 1.05em
+static const css_length_t fallback_normal_line_height = css_length_t(css_val_unspecified, 1*256 + (256 * 2 + 10 / 2) / 10); // 1.2 unitless
 
 int scaleForRenderDPI( int value ) {
     // if gRenderDPI == 0 or 96, use value as is (1px = 1px)
@@ -3131,7 +3135,13 @@ lString32 renderListItemMarker( ldomNode * enode, int & marker_width, int * fina
         if (line_h < 0) { // -1, not specified by caller: find it out from the node
             if ( style->line_height.type == css_val_unspecified &&
                         style->line_height.value == css_generic_normal ) {
-                line_h = font->getHeight(); // line-height: normal
+                int em = font->getSize();
+                if (gRenderMinNormalLineHeight > 0) {
+                    line_h = gRenderMinNormalLineHeight + lengthToPx(enode, relative_normal_line_height, em, em, true);
+                }
+                else {
+                    line_h = font->getHeight(); // line-height: normal
+                }
             }
             else {
                 int em = font->getSize();
@@ -3402,7 +3412,12 @@ void renderFinalBlock( ldomNode * enode, LFormattedText * txform, RenderRectAcce
             // Only "normal" uses enode->getFont()->getHeight()
             if ( style->line_height.type == css_val_unspecified &&
                         style->line_height.value == css_generic_normal ) {
-                line_h = enode->getFont()->getHeight(); // line-height: normal
+                if (gRenderMinNormalLineHeight > 0) {
+                    line_h = gRenderMinNormalLineHeight + lengthToPx(enode, relative_normal_line_height, em, em, true);
+                }
+                else {
+                    line_h = enode->getFont()->getHeight(); // line-height: normal
+                }
             }
             else {
                 // In all other cases (%, em, unitless/unspecified), we can just scale 'em',
@@ -7457,7 +7472,12 @@ void renderBlockElementEnhanced( FlowState * flow, ldomNode * enode, int x, int
             int line_h;
             if ( style->line_height.type == css_val_unspecified &&
                         style->line_height.value == css_generic_normal ) {
-                line_h = enode->getFont()->getHeight(); // line-height: normal
+                if (gRenderMinNormalLineHeight > 0) {
+                    line_h = gRenderMinNormalLineHeight + lengthToPx(enode, relative_normal_line_height, em, em, true);
+                }
+                else {
+                    line_h = enode->getFont()->getHeight(); // line-height: normal
+                }
             }
             else {
                 // In all other cases (%, em, unitless/unspecified), we can just

crengine/src/lvtinydom.cpp

@@ -405,6 +405,7 @@ lUInt32 calcGlobalSettingsHash(int documentId, bool already_rendered)
     // hash = hash * 31 + (int)fontMan->GetHintingMode();
     hash = hash * 31 + LVRendGetBaseFontWeight();
     hash = hash * 31 + gRenderDPI;
+    hash = hash * 31 + gRenderMinNormalLineHeight;
     // If not yet rendered (initial loading with XML parsing), we can
     // ignore some global flags that have not yet produced any effect,
     // so they can possibly be updated between loading and rendering