Merge pull request #807 from mscuthbert/stem_length

Stem length to middle line

src/stavenote.js

@@ -81,7 +81,7 @@ export class StaveNote extends StemmableNote {
       let minL = props[props.length - 1].line;
       const stemDirection = notes[i].getStemDirection();
       const stemMax = notes[i].getStemLength() / 10;
-      const stemMin = notes[i].getStemMinumumLength() / 10;
+      const stemMin = notes[i].getStemMinimumLength() / 10;
 
       let maxL;
       if (notes[i].isRest()) {
@@ -439,6 +439,10 @@ export class StaveNote extends StemmableNote {
 
   // Automatically sets the stem direction based on the keys in the note
   autoStem() {
+    this.setStemDirection(this.calculateOptimalStemDirection());
+  }
+
+  calculateOptimalStemDirection() {
     // Figure out optimal stem direction based on given notes
     this.minLine = this.keyProps[0].line;
     this.maxLine = this.keyProps[this.keyProps.length - 1].line;
@@ -447,7 +451,7 @@ export class StaveNote extends StemmableNote {
     const decider = (this.minLine + this.maxLine) / 2;
     const stemDirection = decider < MIDDLE_LINE ? Stem.UP : Stem.DOWN;
 
-    this.setStemDirection(stemDirection);
+    return stemDirection;
   }
 
   // Calculates and stores the properties for each key in the note
@@ -561,8 +565,8 @@ export class StaveNote extends StemmableNote {
     return new BoundingBox(x, minY, w, maxY - minY);
   }
 
-  // Gets the line number of the top or bottom note in the chord.
-  // If `isTopNote` is `true` then get the top note
+  // Gets the line number of the bottom note in the chord.
+  // If `isTopNote` is `true` then get the top note's line number instead
   getLineNumber(isTopNote) {
     if (!this.keyProps.length) {
       throw new Vex.RERR(
@@ -1106,6 +1110,48 @@ export class StaveNote extends StemmableNote {
     this.context.closeGroup();
   }
 
+
+  /**
+   * Override stemmablenote stem extension to adjust for distance from middle line.
+   */
+  getStemExtension() {
+    const super_stem_extension = super.getStemExtension();
+    if (!this.glyph.stem) {
+      return super_stem_extension;
+    }
+
+    const stem_direction = this.getStemDirection();
+    if (stem_direction !== this.calculateOptimalStemDirection()) {
+      return super_stem_extension;  // no adjustment for manually set stem direction.
+    }
+    let mid_line_distance;
+    const MIDDLE_LINE = 3;
+    if (stem_direction === Stem.UP) {
+      // Note that the use of maxLine here instead of minLine might
+      // seem counterintuitive, but in the case of (say) treble clef
+      // chord(F2, E4) stem up, we do not want to extend the stem because
+      // of F2, when a normal octave-length stem above E4 is fine.
+      //
+      // maxLine and minLine are set in calculateOptimalStemDirection() so
+      // will be known.
+      mid_line_distance = MIDDLE_LINE - this.maxLine;
+    } else {
+      mid_line_distance = this.minLine - MIDDLE_LINE;
+    }
+
+    // how many lines more than an octave is the relevant notehead?
+    const lines_over_octave_from_mid_line = mid_line_distance - 3.5;
+    if (lines_over_octave_from_mid_line <= 0) {
+      return super_stem_extension;
+    }
+    const stave = this.getStave();
+    let spacing_between_lines = 10;
+    if (stave != null) {
+      spacing_between_lines = stave.getSpacingBetweenLines();
+    }
+    return super_stem_extension + (lines_over_octave_from_mid_line * spacing_between_lines);
+  }
+
   // Draws all the `StaveNote` parts. This is the main drawing method.
   draw() {
     if (!this.context) {

src/stem.js

@@ -93,10 +93,16 @@ export class Stem extends Element {
 
   // Gets the entire height for the stem
   getHeight() {
-    const y_offset = (this.stem_direction === Stem.UP) ? this.stem_up_y_offset : this.stem_down_y_offset; // eslint-disable-line max-len
-    return ((this.y_bottom - this.y_top) * this.stem_direction) +
-           ((Stem.HEIGHT - y_offset + this.stem_extension) * this.stem_direction);
+    const y_offset = (this.stem_direction === Stem.UP)
+      ? this.stem_up_y_offset
+      : this.stem_down_y_offset;
+    const unsigned_height = (
+      (this.y_bottom - this.y_top)
+      + (Stem.HEIGHT - y_offset + this.stem_extension)
+    );  // parentheses just for grouping.
+    return unsigned_height * this.stem_direction;
   }
+
   getBoundingBox() {
     throw new Vex.RERR('NotImplemented', 'getBoundingBox() not implemented.');
   }

src/stemmablenote.js

@@ -16,7 +16,7 @@ export class StemmableNote extends Note {
     this.setAttribute('type', 'StemmableNote');
 
     this.stem = null;
-    this.stemExtensionOverride = null;
+    this.stem_extension_override = null;
     this.beam = null;
   }
 
@@ -70,7 +70,7 @@ export class StemmableNote extends Note {
   }
 
   // Get the minimum length of stem
-  getStemMinumumLength() {
+  getStemMinimumLength() {
     const frac = Flow.durationToFraction(this.duration);
     let length = frac.value() <= 1 ? 0 : 20;
     // if note is flagged, cannot shorten beam
@@ -153,12 +153,12 @@ export class StemmableNote extends Note {
   getStemExtension() {
     const glyph = this.getGlyph();
 
-    if (this.stemExtensionOverride != null) {
-      return this.stemExtensionOverride;
+    if (this.stem_extension_override != null) {
+      return this.stem_extension_override;
     }
 
     if (glyph) {
-      return this.getStemDirection() === 1
+      return this.getStemDirection() === Stem.UP
         ? glyph.stem_up_extension
         : glyph.stem_down_extension;
     }
@@ -168,7 +168,7 @@ export class StemmableNote extends Note {
 
   // Set the stem length to a specific. Will override the default length.
   setStemLength(height) {
-    this.stemExtensionOverride = (height - Stem.HEIGHT);
+    this.stem_extension_override = (height - Stem.HEIGHT);
     return this;
   }