Added Division drawable which is a container that can wrap over pages

pdf/creator/division.go

@@ -0,0 +1,136 @@
+/*
+ * This file is subject to the terms and conditions defined in
+ * file 'LICENSE.md', which is part of this source code package.
+ */
+
+package creator
+
+import (
+	"errors"
+
+	"github.com/unidoc/unidoc/common"
+)
+
+// Division is a container component which can wrap across multiple pages (unlike Block).
+// It can contain multiple Drawable components (currently supporting Paragraph and Image).
+//
+// The component stacking behavior is vertical, where the Drawables are drawn on top of each other.
+// TODO: Add inline mode (horizontal stacking).
+type Division struct {
+	components []VectorDrawable
+
+	// Positioning: relative / absolute.
+	positioning positioning
+
+	// Margins to be applied around the block when drawing on Page.
+	margins margins
+}
+
+// NewDivision returns a new Division container component.
+func NewDivision() *Division {
+	div := &Division{}
+	div.components = []VectorDrawable{}
+	return div
+}
+
+// Add adds a VectorDrawable to the Division container.
+// Currently supported VectorDrawables: *Paragraph, *Image.
+func (div *Division) Add(d VectorDrawable) error {
+	supported := false
+
+	switch d.(type) {
+	case *Paragraph:
+		supported = true
+	case *Image:
+		supported = true
+	}
+
+	if !supported {
+		return errors.New("Unsupported type in Division")
+	}
+
+	div.components = append(div.components, d)
+
+	return nil
+}
+
+// Height returns the height for the Division component assuming all stacked on top of each other.
+func (div *Division) Height() float64 {
+	y := 0.0
+	yMax := 0.0
+	for _, component := range div.components {
+		compWidth, compHeight := component.Width(), component.Height()
+		switch t := component.(type) {
+		case *Paragraph:
+			p := t
+			compWidth += p.margins.left + p.margins.right
+			compHeight += p.margins.top + p.margins.bottom
+		}
+
+		// Vertical stacking.
+		y += compHeight
+		yMax = y
+	}
+
+	return yMax
+}
+
+// Width is not used. Not used as a Division element is designed to fill into available width depending on
+// context.  Returns 0.
+func (div *Division) Width() float64 {
+	return 0
+}
+
+// GeneratePageBlocks generates the page blocks for the Division component.
+// Multiple blocks are generated if the contents wrap over multiple pages.
+func (div *Division) GeneratePageBlocks(ctx DrawContext) ([]*Block, DrawContext, error) {
+	pageblocks := []*Block{}
+
+	origCtx := ctx
+
+	if div.positioning.isRelative() {
+		// Update context.
+		ctx.X += div.margins.left
+		ctx.Y += div.margins.top
+		ctx.Width -= div.margins.left + div.margins.right
+		ctx.Height -= div.margins.top
+	}
+
+	// Draw.
+	for _, component := range div.components {
+		newblocks, updCtx, err := component.GeneratePageBlocks(ctx)
+		if err != nil {
+			common.Log.Debug("Error generating page blocks: %v", err)
+			return nil, ctx, err
+		}
+
+		if len(newblocks) < 1 {
+			continue
+		}
+
+		if len(pageblocks) > 0 {
+			// If there are pageblocks already in place.
+			// merge the first block in with current Block and append the rest.
+			pageblocks[len(pageblocks)-1].mergeBlocks(newblocks[0])
+			pageblocks = append(pageblocks, newblocks[1:]...)
+		} else {
+			pageblocks = append(pageblocks, newblocks[0:]...)
+		}
+
+		// Apply padding/margins.
+		updCtx.X = ctx.X
+		ctx = updCtx
+	}
+
+	if div.positioning.isRelative() {
+		// Move back X to same start of line.
+		ctx.X = origCtx.X
+	}
+
+	if div.positioning.isAbsolute() {
+		// If absolute: return original context.
+		return pageblocks, origCtx, nil
+	}
+
+	return pageblocks, ctx, nil
+}