MCGR: Border restoration support

Due to tdf#155362 I added code to be able in case we
would need it to convert a BGradient using added
tooling from having offsets in the GradientSteps
and no border to adapted GradientSteps and border.

This is preferrable due to our GradientStyle_RECT
(and GradientStyle_ELLIPTICAL too) use that 'non-
linear' paint aka move-two-pixels-inside, someone
else called it 'frame-paint'. This does not bode
well with the border being applied 'linear' at the
same time (argh). Thus - while in principle all is
correct when re-importing a GradientStyle_RECT
with a border after export to pptx, it looks
slightly better ('correcter') wen doing so. That is
because when being able to and restoring a border
at least that border part *is* applied linearly.

I took the chance to further apply tooling, move
it to classes involved and instead of awt::Gradient2
use more basegfx::BGradient since it can and does
host tooling. This is also a preparation to be
able to adapt (restore) border in case of turn-
around in ODF where the importing instance is before
MCGR existance and has to handle Start/EndColor.

Needed to take more care with using BGradient instead
of awt::Gradient2 for initialization, also better
dividing/organization of tooling, already preparation
to use for other purposes.

Change-Id: I2d3a4240a5ac6fff9211b46642ee80366dc09e3d
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/152194
Tested-by: Jenkins
Reviewed-by: Armin Le Grand <Armin.Le.Grand@me.com>

2 files changed, 30 insertions, 10 deletions

diff --git a/include/basegfx/utils/bgradient.hxx b/include/basegfx/utils/bgradient.hxx
index a0e853ec7099..fa9591cdb266 100644
--- a/include/basegfx/utils/bgradient.hxx
+++ b/include/basegfx/utils/bgradient.hxx
@@ -40,13 +40,10 @@ namespace basegfx
 
         Offset is defined as:
         - being in the range of [0.0 .. 1.0] (unit range)
-          - 0.0 being reserved for StartColor
-          - 1.0 being reserved for EndColor
-        - in-between offsets thus being in the range of ]0.0 .. 1.0[
-        - no two equal offsets are allowed
-            - this is an error
-        - missing 1.0 entry (EndColor) is allowed
-          - it means that EndColor == StartColor
+          - offsets outside are an error
+        - lowest/1st value equivalent to StartColor
+        - highest/last value equivalent to EndColor
+        - missing 0.0/1.0 entries are allowed
         - at least one value (usually 0.0, StartColor) is required
             - this allows to avoid massive testing in all places where
               this data has to be accessed
@@ -263,6 +260,19 @@ public:
            When also mirroring offsets a valid sort keeps valid.
         */
     void reverseColorStops();
+
+    // createSpaceAtStart creates fOffset space at start by
+    // translating/scaling all entries to the right
+    void createSpaceAtStart(double fOffset);
+
+    // removeSpaceAtStart removes fOffset space from start by
+    // translating/scaling entries more or equal to fOffset
+    // to the left. Entries less than fOffset will be removed
+    void removeSpaceAtStart(double fOffset);
+
+    // try to detect if an empty/no-color-change area exists
+    // at the start and return offset to it. Returns 0.0 if not.
+    double detectPossibleOffsetAtStart() const;
 };
 
 class BASEGFX_DLLPUBLIC BGradient final
@@ -323,6 +333,11 @@ public:
 
     /// Tooling method to fill awt::Gradient2 from data contained in the given basegfx::BGradient
     css::awt::Gradient2 getAsGradient2() const;
+
+    /// Tooling to handle border correction/integration and StartStopIntensity
+    void tryToRecreateBorder(basegfx::BColorStops* pAssociatedTransparencyStops);
+    void tryToApplyBorder();
+    void tryToApplyStartEndIntensity();
 };
 }
 
diff --git a/include/basegfx/utils/gradienttools.hxx b/include/basegfx/utils/gradienttools.hxx
index 9672259be64b..6fc51adc0e37 100644
--- a/include/basegfx/utils/gradienttools.hxx
+++ b/include/basegfx/utils/gradienttools.hxx
@@ -186,18 +186,23 @@ namespace basegfx
 
     namespace utils
     {
-        /* Tooling method to extract data from given awt::Gradient2
+        /* Tooling method to extract data from given BGradient
            to ColorStops, doing some corrections, partially based
            on given SingleColor.
+           This is used for export preparations in case these exports
+           do neither support Start/EndIntensity nor Border settings,
+           both will be elliminated if possible (see below).
+           The BGradient rGradient and BColorStops& rColorStops
+           are both return parameters and may be changed.
            This will do quite some preparations for the gradient
            as follows:
            - It will check for single color (resetting rSingleColor when
              this is the case) and return with empty ColorStops
            - It will blend ColorStops to Intensity if StartIntensity/
-             EndIntensity != 100 is set in awt::Gradient2, so applying
+             EndIntensity != 100 is set in BGradient, so applying
              that value(s) to the gradient directly
            - It will adapt to Border if Border != 0 is set at the
-             given awt::Gradient2, so applying that value to the gradient
+             given BGradient, so applying that value to the gradient
              directly
         */
         BASEGFX_DLLPUBLIC void prepareColorStops(