[release-branch.go1.3] go.tools/present: allow intentionally empty parameters
««« CL 105070043 / 1e6e75afb0cd
go.tools/present: allow intentionally empty parameters
Fixes golang/go#7613.
LGTM=r
R=adg, r
CC=golang-codereviews
https://golang.org/cl/105070043
»»»
LGTM=dsymonds
R=dsymonds
CC=golang-codereviews
https://golang.org/cl/148300043
diff --git a/present/code.go b/present/code.go
index 2816a87..a176435 100644
--- a/present/code.go
+++ b/present/code.go
@@ -238,6 +238,8 @@
res[i] = v
case '$':
res[i] = "$"
+ case '_':
+ // Do nothing; '_' indicates an intentionally empty parameter.
default:
return nil, fmt.Errorf("%s:%d bad code argument %q", name, line, v)
}
diff --git a/present/doc.go b/present/doc.go
index afd50e7..da71e8d 100644
--- a/present/doc.go
+++ b/present/doc.go
@@ -168,10 +168,14 @@
The syntax is simple: 1 or 3 space-separated arguments.
The first argument is always the file name.
If there are more arguments, they are the height and width;
-both must be present.
+both must be present, or substituted with an underscore.
+Replacing a dimension argument with the underscore parameter
+preserves the aspect ratio of the image when scaling.
.image images/betsy.jpg 100 200
+ .image images/janet.jpg _ 300
+
iframe:
The function "iframe" injects iframes (pages inside pages).
diff --git a/present/image.go b/present/image.go
index 2bab429..cfa2af9 100644
--- a/present/image.go
+++ b/present/image.go
@@ -32,6 +32,11 @@
case 0:
// no size parameters
case 2:
+ // If a parameter is empty (underscore) or invalid
+ // leave the field set to zero. The "image" action
+ // template will then omit that img tag attribute and
+ // the browser will calculate the value to preserve
+ // the aspect ratio.
if v, ok := a[0].(int); ok {
img.Height = v
}
