From 10e284c92972bbc8148e098eb8172798ffae4ebc Mon Sep 17 00:00:00 2001
From: Leon Styhre <leon@leonstyhre.com>
Date: Thu, 14 Oct 2021 21:59:09 +0200
Subject: [PATCH] Text in ScrollableContainer now mostly stays within the
 initial area.

---
 es-core/src/components/ScrollableContainer.cpp | 11 +++++++++++
 es-core/src/components/ScrollableContainer.h   |  1 +
 2 files changed, 12 insertions(+)

diff --git a/es-core/src/components/ScrollableContainer.cpp b/es-core/src/components/ScrollableContainer.cpp
index 218b7cd3a..51f33f917 100644
--- a/es-core/src/components/ScrollableContainer.cpp
+++ b/es-core/src/components/ScrollableContainer.cpp
@@ -18,6 +18,7 @@ ScrollableContainer::ScrollableContainer(Window* window)
     : GuiComponent{window}
     , mScrollPos{0.0f, 0.0f}
     , mScrollDir{0.0f, 0.0f}
+    , mClipSpacing{0.0f}
     , mAutoScrollDelay{0}
     , mAutoScrollSpeed{0}
     , mAutoScrollAccumulator{0}
@@ -81,6 +82,11 @@ void ScrollableContainer::update(int deltaTime)
     float lineSpacing{mChildren.front()->getLineSpacing()};
     float combinedHeight{mChildren.front()->getFont()->getHeight(lineSpacing)};
 
+    // Calculate the line spacing which will be used to clip the container.
+    if (mClipSpacing == 0.0f)
+        mClipSpacing =
+            std::round((combinedHeight - mChildren.front()->getFont()->getLetterHeight()) / 2.0f);
+
     // Resize container to font height boundary to avoid rendering a fraction of the last line.
     if (!mUpdatedSize && contentSize.y > mSize.y) {
         float numLines{mSize.y / combinedHeight};
@@ -173,6 +179,11 @@ void ScrollableContainer::render(const glm::mat4& parentTrans)
     glm::ivec2 clipDim{static_cast<int>(dimScaled.x - trans[3].x),
                        static_cast<int>(dimScaled.y - trans[3].y)};
 
+    // By effectively clipping the upper and lower boundaries of the container we mostly avoid
+    // scrolling outside the vertical starting and ending positions.
+    clipPos.y += mClipSpacing;
+    clipDim.y -= mClipSpacing * 0.9f;
+
     Renderer::pushClipRect(clipPos, clipDim);
 
     trans = glm::translate(trans, -glm::vec3{mScrollPos.x, mScrollPos.y, 0.0f});
diff --git a/es-core/src/components/ScrollableContainer.h b/es-core/src/components/ScrollableContainer.h
index 27b63f459..fb80b7eea 100644
--- a/es-core/src/components/ScrollableContainer.h
+++ b/es-core/src/components/ScrollableContainer.h
@@ -44,6 +44,7 @@ private:
     float mAutoScrollDelayConstant;
     float mAutoScrollSpeedConstant;
     float mResolutionModifier;
+    float mClipSpacing;
 
     int mAutoScrollDelay;
     int mAutoScrollSpeed;