Adding code to calculate Underline Thickness from Font Metrics, this will be useful when Skia is us…

include/core/SkPaint.h

Index: include/core/SkPaint.h
diff --git a/include/core/SkPaint.h b/include/core/SkPaint.h
index abb859950c5bb6a66aecccded690ca8cd6ae02a2..1887c7f6175acea3a1291680fe5ae4d21e1ca731 100644
--- a/include/core/SkPaint.h
+++ b/include/core/SkPaint.h
@@ -730,7 +730,28 @@ public:
 
     void setTextEncoding(TextEncoding encoding);
 
+    /** Describes defined to identify which values are unknown, later can be
+        used for other uses
+    */
+    enum FontMetricsBitSet {

[reed1, 2014/02/12 17:29:08]

Skia convention would name this FontMetricsFlags, and then use that as a suffix

e.g.

kUnderlineIsValid_FontMetricFlag = 1 << ...,

[reed1, 2014/02/12 17:29:08]

Possibly we could place this enum inside FontMetrics itself, making it...

struct FontMetrics {
    enum Flags {
        ...
    };

[h.joshi, 2014/02/13 02:23:52]

Okey, will change enum variable names.

On 2014/02/12 17:29:08, reed1 wrote:

[h.joshi, 2014/02/13 02:23:52]

Okey, will shift emum inside FontMetrics structure.

On 2014/02/12 17:29:08, reed1 wrote:

+        kFontMetrics_Top = 1 << 1,                  //!< Bit flag for FontMetrics fTop
+        kFontMetrics_Ascent = 1 << 2,               //!< Bit flag for FontMetrics Ascent
+        kFontMetrics_Descent = 1 << 3,              //!< Bit flag for FontMetrics Descent
+        kFontMetrics_Bottom = 1 << 4,               //!< Bit flag for FontMetrics Bottom

[reed1, 2014/02/12 17:29:08]

Do we really need/want a bit for every field? I thought only underline was in
question here.

The comment on each line may be unnecessary -- it doesn't say anything that
isn't quite clear from the enum name.

[h.joshi, 2014/02/13 02:43:20]

Will remove comments from enum.
Underline will get assigned similar to Ascent etc variables, so added emum for
all. Pls suggest how should I follow up here.

On 2014/02/12 17:29:08, reed1 wrote:

+        kFontMetrics_Leading = 1 << 5,              //!< Bit flag for FontMetrics Leading
+        kFontMetrics_AvgCharWidth = 1 << 6,         //!< Bit flag for FontMetrics Average Char Width
+        kFontMetrics_MaxCharWidth = 1 << 7,         //!< Bit flag for FontMetrics Max Char Width
+        kFontMetrics_XMin = 1 << 8,                 //!< Bit flag for FontMetrics x - min
+        kFontMetrics_XMax = 1 << 9,                 //!< Bit flag for FontMetrics x - max
+        kFontMetrics_XHeight = 1 << 10,             //!< Bit flag for FontMetrics x - height
+        kFontMetrics_CapHeight = 1 << 11,           //!< Bit flag for FontMetrics Cap Height
+        kFontMetrics_UnderlineThickness = 1 << 12,  //!< Bit flag for FontMetrics Underline Thickness
+        kFontMetrics_UnderlinePosition = 1 << 13,   //!< Bit flag for FontMetrics Underline Position
+        kFontMetrics_Max = 0xFFFF,                 //!< Max Bit flag

[reed1, 2014/02/12 17:29:08]

Why do we need the Max?

[h.joshi, 2014/02/13 02:23:52]

Just added to signify for max/default value, thinking maybe if required in
future. Should I remove this?

On 2014/02/12 17:29:08, reed1 wrote:

+    };
+
     struct FontMetrics {
+        uint16_t    fFontMetricsFlag;       //!< Bit field to identify which values are unknown

[reed1, 2014/02/12 17:29:08]

definitely make this uint32_t (or possibly 64bit) for alignment (and future
proofing).

[h.joshi, 2014/02/13 02:23:52]

Okey will make it 32 bit.

On 2014/02/12 17:29:08, reed1 wrote:

         SkScalar    fTop;       //!< The greatest distance above the baseline for any glyph (will be <= 0)
         SkScalar    fAscent;    //!< The recommended distance above the baseline (will be <= 0)
         SkScalar    fDescent;   //!< The recommended distance below the baseline (will be >= 0)
@@ -742,8 +763,17 @@ public:
         SkScalar    fXMax;      //!< The maximum bounding box x value for all glyphs
         SkScalar    fXHeight;   //!< The height of an 'x' in px, or 0 if no 'x' in face
         SkScalar    fCapHeight;  //!< The cap height (> 0), or 0 if cannot be determined.
+        SkScalar    fUnderlineThickness; //!< underline thickness, or 0 if cannot be determined
+        SkScalar    fUnderlinePosition; //!< underline position, or 0 if cannot be determined
     };
 
+   /** Method to get bit set for Font Metrics
+        @param fObject Pointer of FontMetrics object
+        @param bitSet  bit whose value we want to know is set or not
+        @param retrun true if FontMetrics bit i set false otherwise
+    */
+    bool isFontMetricsBitSet(FontMetrics * fObject, FontMetricsBitSet bitSet) const;
+
     /** Return the recommend spacing between lines (which will be
         fDescent - fAscent + fLeading).
         If metrics is not null, return in it the font metrics for the