present: add support for quote

cmd/present/static/styles.css

@@ -532,3 +532,12 @@ figcaption {
   -moz-border-radius: 10px;
   -webkit-border-radius: 10px;
 }
+
+blockquote {
+  padding: 5px 20px;
+  border-left: 5px solid #999;
+}
+blockquote cite {
+  font-size: 85%;
+  color: #999;
+}

cmd/present/templates/action.tmpl

@@ -60,3 +60,10 @@ It determines how the formatting actions are rendered.
 {{define "html"}}{{.HTML}}{{end}}
 
 {{define "caption"}}<figcaption>{{style .Text}}</figcaption>{{end}}
+
+{{define "quote"}}
+<blockquote>
+  <p>{{style .Text}}</p>
+  {{with .Citation}}<cite>&mdash; {{style .}}</cite>{{end}}
+</blockquote>
+{{end}}

present/doc.go

@@ -63,6 +63,7 @@ After that come slides/sections, each after a blank line:
 	.link http://foo label
 	.html file.html
 	.caption _Gopher_ by [[https://www.instagram.com/reneefrench/][Renée French]]
+	.quote Never memorize something that you can look up //CITATION: Albert Einstein
 
 	Again, more text
 
@@ -214,6 +215,16 @@ processing styling and links as in standard text lines.
 
 	.caption _Gopher_ by [[http://www.reneefrench.com][Renée French]]
 
+quote:
+
+The template uses the function "quote" to inject quotes and citations.
+
+The text after ".quote" is embedded in a blockquote element after
+processing styling. The text after the optional "//CITATION:" is treated
+as a citation and embedded in a cite element after processing styling.
+
+	.quote Never memorize something that you can look up //CITATION: Albert Einstein
+
 iframe:
 
 The function "iframe" injects iframes (pages inside pages).

present/quote.go

@@ -0,0 +1,50 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package present
+
+import (
+	"fmt"
+	"strings"
+)
+
+func init() {
+	Register("quote", parseQuote)
+}
+
+type Quote struct {
+	Text     string
+	Citation string
+}
+
+func (c Quote) TemplateName() string { return "quote" }
+
+const citationToken = "//CITATION:"
+
+// parseQuote parses a quote present directive. Its syntax:
+//   .quote <text> [citation]
+func parseQuote(_ *Context, sourceFile string, sourceLine int, cmd string) (Elem, error) {
+
+	cmd = strings.TrimSpace(strings.TrimPrefix(cmd, ".quote"))
+
+	tokens := strings.Split(cmd, citationToken)
+
+	text := strings.TrimSpace(strings.TrimPrefix(tokens[0], ".quote"))
+	citation := ""
+
+	if text == "" {
+		return nil, fmt.Errorf("%s:%d invalid quote syntax", sourceFile, sourceLine)
+	}
+
+	if len(tokens) == 1 {
+		return Quote{text, citation}, nil
+	}
+
+	citation = strings.TrimSpace(tokens[1])
+	if citation == "" || len(tokens) > 2 {
+		return nil, fmt.Errorf("%s:%d invalid citation syntax", sourceFile, sourceLine)
+	}
+
+	return Quote{text, citation}, nil
+}

present/quote_test.go

@@ -0,0 +1,78 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package present
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestQuoteParsing(t *testing.T) {
+	var tests = []struct {
+		name string
+		cmd  string
+		err  string
+		Quote
+	}{
+		{
+			name: "quote with invalid citation syntax",
+			cmd:  ".quote a quote //CITATION: ",
+			err:  "invalid citation syntax",
+		},
+		{
+			name: "quote without text and valid citation",
+			cmd:  ".quote //CITATION: citation",
+			err:  "invalid quote syntax",
+		},
+		{
+			name: "quote with text",
+			cmd:  ".quote some text",
+			Quote: Quote{
+				Text:     "some text",
+				Citation: "",
+			},
+		},
+		{
+			name: "quote with text and citation",
+			cmd:  ".quote some text //CITATION: other text",
+			Quote: Quote{
+				Text:     "some text",
+				Citation: "other text",
+			},
+		},
+	}
+
+	for _, test := range tests {
+		element, err := parseQuote(nil, "test.slide", 0, test.cmd)
+
+		if err != nil {
+			if test.err == "" {
+				t.Errorf("%s: unexpected error %v", test.name, err)
+			} else if !strings.Contains(err.Error(), test.err) {
+				t.Errorf("%s: expected error %s; got %v", test.name, test.err, err)
+			}
+			continue
+		}
+
+		if test.err != "" {
+			t.Errorf("%s: expected error %s; but got none", test.name, test.err)
+			continue
+		}
+
+		quote, ok := element.(Quote)
+		if !ok {
+			t.Errorf("%s: expected a Code value; got %T", test.name, quote)
+			continue
+		}
+
+		if quote.Text != test.Text {
+			t.Errorf("%s: expected Text %s; got %s", test.name, test.Text, quote.Text)
+		}
+
+		if quote.Citation != test.Citation {
+			t.Errorf("%s: expected Citation %s; got %s", test.name, test.Citation, quote.Citation)
+		}
+	}
+}