adding a way to allow large pdfs to zoom to the correct size (Univers…

…alViewer#742)

src/modules/uv-pdfcenterpanel-module/PDFCenterPanel.ts

@@ -314,6 +314,25 @@ export class PDFCenterPanel extends CenterPanel {
             this._canvas.height = this._viewport.height;
             this._canvas.width = this._viewport.width;
 
+
+            // get divisible number between canvas height and content height
+            const divisible_amount = this._canvas.height / this.$content.height()
+            // create a variable for the new canvas height.
+            // (canvas height divided by our divisible_amount) multiply by the viewport scale
+            var canvas_height = (this._canvas.height / divisible_amount) * this._viewport.scale;
+
+            // if canvas height is smaller than our content height
+            // use the content hight instead
+            if(canvas_height < this.$content.height()) {
+                canvas_height = this.$content.height();
+            }
+
+            // set the canvas height with CSS
+            this._$canvas.css({
+                height: canvas_height
+            });
+
+
             // Render PDF page into canvas context
             const renderContext = {
                 canvasContext: this._ctx,