From cbbfe21f94ea53f0800feaf4e9c06c038ddc1e6e Mon Sep 17 00:00:00 2001
From: Kurt Jung <kurt.w.jung@code.google.com>
Date: Tue, 16 Sep 2014 22:38:49 -0400
Subject: Added layer functionality. This allows content to be placed into
 layers, the visibility of which can be controlled from the document reader.

---
 layer.go | 123 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 123 insertions(+)
 create mode 100644 layer.go

(limited to 'layer.go')

diff --git a/layer.go b/layer.go
new file mode 100644
index 0000000..d567e37
--- /dev/null
+++ b/layer.go
@@ -0,0 +1,123 @@
+/*
+ * Copyright (c) 2014 Kurt Jung (Gmail: kurt.w.jung)
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+package gofpdf
+
+// Routines in this file are translated from
+// http://www.fpdf.org/en/script/script97.php
+
+type layerType struct {
+	name    string
+	visible bool
+	objNum  int // object number
+}
+
+type layerRecType struct {
+	list          []layerType
+	currentLayer  int
+	openLayerPane bool
+}
+
+func (f *Fpdf) layerInit() {
+	f.layer.list = make([]layerType, 0)
+	f.layer.currentLayer = -1
+	f.layer.openLayerPane = false
+}
+
+// AddLayer defines a layer that can be shown or hidden when the document is
+// displayed. name specifies the layer name that the document reader will
+// display in the layer list. visible specifies whether the layer will be
+// initially visible. The return value is an integer ID that is used in a call
+// to BeginLayer().
+//
+// Layers are demonstrated in tutorial 26.
+func (f *Fpdf) AddLayer(name string, visible bool) (layerID int) {
+	layerID = len(f.layer.list)
+	f.layer.list = append(f.layer.list, layerType{name: name, visible: visible})
+	return
+}
+
+// BeginLayer is called to begin adding content to the specified layer. All
+// content added to the page between a call to BeginLayer and a call to
+// EndLayer is added to the layer specified by id. See AddLayer for more
+// details.
+func (f *Fpdf) BeginLayer(id int) {
+	f.EndLayer()
+	if id >= 0 && id < len(f.layer.list) {
+		f.outf("/OC /OC%d BDC", id)
+		f.layer.currentLayer = id
+	}
+}
+
+// EndLayer is called to stop adding content to the currently active layer. See
+// BeginLayer for more details.
+func (f *Fpdf) EndLayer() {
+	if f.layer.currentLayer >= 0 {
+		f.out("EMC")
+		f.layer.currentLayer = -1
+	}
+}
+
+// OpenLayerPane advises the document reader to open the layer pane when the
+// document is initially displayed.
+func (f *Fpdf) OpenLayerPane() {
+	f.layer.openLayerPane = true
+}
+
+func (f *Fpdf) layerEndDoc() {
+	if len(f.layer.list) > 0 {
+		if f.pdfVersion < "1.5" {
+			f.pdfVersion = "1.5"
+		}
+	}
+}
+
+func (f *Fpdf) layerPutLayers() {
+	for j, l := range f.layer.list {
+		f.newobj()
+		f.layer.list[j].objNum = f.n
+		f.outf("<</Type /OCG /Name %s>>", f.textstring(utf8toutf16(l.name)))
+		f.out("endobj")
+	}
+}
+
+func (f *Fpdf) layerPutResourceDict() {
+	if len(f.layer.list) > 0 {
+		f.out("/Properties <<")
+		for j, layer := range f.layer.list {
+			f.outf("/OC%d %d 0 R", j, layer.objNum)
+		}
+		f.out(">>")
+	}
+
+}
+
+func (f *Fpdf) layerPutCatalog() {
+	if len(f.layer.list) > 0 {
+		onStr := ""
+		offStr := ""
+		for _, layer := range f.layer.list {
+			onStr += sprintf("%d 0 R ", layer.objNum)
+			if !layer.visible {
+				offStr += sprintf("%d 0 R ", layer.objNum)
+			}
+		}
+		f.outf("/OCProperties <</OCGs [%s] /D <</OFF [%s] /Order [%s]>>>>", onStr, offStr, onStr)
+		if f.layer.openLayerPane {
+			f.out("/PageMode /UseOC")
+		}
+	}
+}
-- 
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