add line-breaking algorithm initially

[clo] / src / libclo / breakLines.ts

diff --git a/src/libclo/breakLines.ts b/src/libclo/breakLines.ts
new file mode 100644 (file)
index 0000000..989ba93
--- /dev/null
+++ b/src/libclo/breakLines.ts
@@ -0,0 +1,109 @@
+/**
+ * Algorithms and functions for LineBreaking
+ */
+import { join } from "path";
+import {BreakPoint, BoxesItem, HGlue} from "./index.js";
+/** 
+ * Algorithms in LATEX language
+TotalCost(i) = min_{j}~TotalCost(j) + LineCost(j, i)~~~~j=0, 1, ..., i-1
+
+LineCost(j, i)= \begin{cases} 
+\infty ~~~ if~~LineWidth - \sum_{k=j+1}^{i-1} OrigWidth(item[k]) - newLineWidth(item[i]) < 0 \\
+\infty~~if~~NOT~~breakable(item[i]) \\
+(LineWidth - \sum_{k=j+1}^{i-1} OrigWidth(item[k]) - newLineWidth(item[i]))^3 ~~elsewhere
+\end{cases} */
+
+/**check if a boeitem is BreakPoint Type */
+function isBreakPoint (item : any) : item is BreakPoint{
+    return (item as BreakPoint).newLined !== undefined;
+}
+
+/**check if a boeitem is BreakPoint Type */
+function isHGlue (item : any) : item is HGlue{
+    return (item as HGlue).stretchFactor !== undefined;
+}
+
+
+/** measuring original advance width */
+function origWidth(item : BoxesItem) : number{
+    if (isBreakPoint(item)){
+        console.log(item);
+        return origWidth(item.original);
+    }else if(Array.isArray(item)){
+        return item.map((x)=>origWidth(x))
+            .reduce((acc, current) => acc + current,
+            0.0,)
+    }else if(isHGlue(item)){
+        return 0.0;
+    }
+    else{
+        return item.width;
+    }
+}
+
+/** measuring new-line triggered advance width */
+function newLineWidth(item : BoxesItem) : number{
+    if (isBreakPoint(item)){
+        return origWidth(item.newLined);
+    }else{
+        // impossible to make a new line
+        return Infinity;
+    }
+}
+
+let lineCostStorage : any = new Object();
+
+/**
+ * check the total cost item[0..j].
+ * @param items 
+ * @param i 
+ * @param lineWidth 
+ */
+export function totalCost(items : BoxesItem[], j : number, lineWidth: number){
+    if (j in lineCostStorage){
+        return lineCostStorage[j];
+    }
+    var returnCost = Infinity;
+    
+    for(var i=-1; i<=j; i++){
+        // lineCost
+        let lCost = lineCost(items, i, j, lineWidth);
+
+        if (returnCost > lCost){
+            returnCost = lCost;
+        }
+    }
+
+    lineCostStorage[j] = returnCost;
+    return returnCost;
+
+}
+
+
+
+/**
+ * check the line cost of a line containing items[i+1..j]
+ * @param items items of box
+ * @param i beginning (excluded)
+ * @param j end of the line 
+ * @param lineWidth line width
+ */
+function lineCost(items : BoxesItem[], i : number, j : number, lineWidth: number){
+    if (!isBreakPoint(items[j])){
+        return Infinity;
+    }else{
+        var tmpItemWidth = 0;
+        for (var k = i+1; k<j; k++){
+            tmpItemWidth += origWidth(items[k]);
+        }
+
+        tmpItemWidth += newLineWidth(items[j]);
+
+        if (tmpItemWidth > lineWidth){
+            return Infinity;
+        }else{
+            return (lineWidth - tmpItemWidth)**3.0;
+        }
+    }
+
+}
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