[LyX/master] Draw a small red frame around preview images that are too small.

[Richard Heck]

commit 7765b1c9a8673d06e84709f787b720f4df6cf00f
Author: Richard Heck <rgh...@lyx.org>
Date:   Wed Mar 19 12:43:21 2014 -0400

    Draw a small red frame around preview images that are too small.

diff --git a/src/mathed/InsetMathHull.cpp b/src/mathed/InsetMathHull.cpp
index e994d44..4c20625 100644
--- a/src/mathed/InsetMathHull.cpp
+++ b/src/mathed/InsetMathHull.cpp
@@ -44,6 +44,7 @@
 #include "insets/InsetRef.h"
 #include "insets/RenderPreview.h"
 
+#include "graphics/GraphicsImage.h"
 #include "graphics/PreviewImage.h"
 #include "graphics/PreviewLoader.h"
 
@@ -410,7 +411,7 @@ ColorCode InsetMathHull::standardColor() const
 }
 
 
-bool InsetMathHull::previewState(BufferView * bv) const
+bool InsetMathHull::previewState(const BufferView *const bv) const
 {
        if (!editing(bv) && RenderPreview::status() == LyXRC::PREVIEW_ON
                && type_ != hullRegexp)
@@ -423,14 +424,24 @@ bool InsetMathHull::previewState(BufferView * bv) const
 }
 
 
+namespace {
+static const int ERROR_FRAME_WIDTH = 2;
+}
+
 void InsetMathHull::metrics(MetricsInfo & mi, Dimension & dim) const
 {
        if (previewState(mi.base.bv)) {
                preview_->metrics(mi, dim);
-               // insert a one pixel gap in front of the formula
-               dim.wid += 1;
-               if (display())
-                       dim.des += displayMargin();
+               if (previewTooSmall(dim)) {
+                       // preview image is too small
+                       dim.wid += 2 * ERROR_FRAME_WIDTH;
+                       dim.asc += 2 * ERROR_FRAME_WIDTH;
+               } else {
+                       // insert a one pixel gap in front of the formula
+                       dim.wid += 1;
+                       if (display())
+                               dim.des += displayMargin();
+               }
                // Cache the inset dimension.
                setDimCache(mi, dim);
                return;
@@ -471,10 +482,21 @@ void InsetMathHull::metrics(MetricsInfo & mi, Dimension & 
dim) const
 }
 
 
+bool InsetMathHull::previewTooSmall(Dimension const & dim) const
+{
+       return dim.width() <= 10 && dim.height() <= 10;
+}
+
+
 ColorCode InsetMathHull::backgroundColor(PainterInfo const & pi) const
 {
-       if (previewState(pi.base.bv))
+       BufferView const * const bv = pi.base.bv;
+       if (previewState(bv)) {
+               Dimension const dim = dimension(*pi.base.bv);
+               if (previewTooSmall(dim))
+                       return Color_error;
                return graphics::PreviewLoader::backgroundColor();
+       }
        return Color_mathbg;
 }
 
@@ -482,23 +504,36 @@ ColorCode InsetMathHull::backgroundColor(PainterInfo 
const & pi) const
 void InsetMathHull::drawBackground(PainterInfo & pi, int x, int y) const
 {
        Dimension const dim = dimension(*pi.base.bv);
+       if (previewTooSmall(dim)) {
+               pi.pain.fillRectangle(x, y - 2 * ERROR_FRAME_WIDTH, 
+                   dim.wid, dim.asc + dim.des, backgroundColor(pi));
+               return;
+       } 
        pi.pain.fillRectangle(x + 1, y - dim.asc + 1, dim.wid - 2,
-               dim.asc + dim.des - 1, pi.backgroundColor(this));
+                       dim.asc + dim.des - 1, backgroundColor(pi));
 }
 
 
 void InsetMathHull::draw(PainterInfo & pi, int x, int y) const
 {
-       use_preview_ = previewState(pi.base.bv);
+       BufferView const * const bv = pi.base.bv;
+       use_preview_ = previewState(bv);
 
        if (type_ == hullRegexp) {
-               Dimension const dim = dimension(*pi.base.bv);
+               Dimension const dim = dimension(*bv);
                pi.pain.rectangle(x + 1, y - dim.ascent() + 1,
                        dim.width() - 2, dim.height() - 2, Color_regexpframe);
        }
+
        if (use_preview_) {
-               // one pixel gap in front
-               preview_->draw(pi, x + 1, y);
+               Dimension const dim = dimension(*bv);
+               if (previewTooSmall(dim)) {
+                       // we have an extra frame
+                       preview_->draw(pi, x + ERROR_FRAME_WIDTH, y);
+               } else {
+                       // one pixel gap in front
+                       preview_->draw(pi, x + 1, y);
+               }
                setPosCache(pi, x, y);
                return;
        }
diff --git a/src/mathed/InsetMathHull.h b/src/mathed/InsetMathHull.h
index af00eaf..0cffffd 100644
--- a/src/mathed/InsetMathHull.h
+++ b/src/mathed/InsetMathHull.h
@@ -271,7 +271,9 @@ protected:
        ///
        void handleFont2(Cursor & cur, docstring const & arg);
        ///
-       bool previewState(BufferView * bv) const;
+       bool previewState(BufferView const * const bv) const;
+       ///
+       bool previewTooSmall(Dimension const & dim) const;
 };