From 11dab2e63ec47ff7866716bf36fa488793de6f9c Mon Sep 17 00:00:00 2001
From: "Valeriano A.R" <valen.alfonso@gmail.com>
Date: Sun, 5 Feb 2017 01:07:58 +0100
Subject: [PATCH] DoubleBufferPanel: Panel with double buffer and utility
 functions.

---
 CsvView.csproj           |  3 +++
 DoubleBufferPanel.cs     | 41 ++++++++++++++++++++++++++++++++++++++++
 FrmCsvViewer.Designer.cs |  8 ++++----
 FrmCsvViewer.cs          | 33 +++++++++++++++++++++-----------
 4 files changed, 70 insertions(+), 15 deletions(-)
 create mode 100644 DoubleBufferPanel.cs

diff --git a/CsvView.csproj b/CsvView.csproj
index 1c73f06..e2abc3f 100644
--- a/CsvView.csproj
+++ b/CsvView.csproj
@@ -50,6 +50,9 @@
     <Compile Include="CTextBox.cs">
       <SubType>Component</SubType>
     </Compile>
+    <Compile Include="DoubleBufferPanel.cs">
+      <SubType>Component</SubType>
+    </Compile>
     <Compile Include="FrmCsvViewer.cs">
       <SubType>Form</SubType>
     </Compile>
diff --git a/DoubleBufferPanel.cs b/DoubleBufferPanel.cs
new file mode 100644
index 0000000..531c0ed
--- /dev/null
+++ b/DoubleBufferPanel.cs
@@ -0,0 +1,41 @@
+using System;
+using System.Runtime.InteropServices;
+using System.Windows.Forms;
+
+namespace CsvView
+{
+    public class DoubleBufferPanel : Panel
+    {
+        public DoubleBufferPanel()
+        {
+            DoubleBuffered = true;
+            SetStyle(ControlStyles.UserPaint |
+                          ControlStyles.AllPaintingInWmPaint |
+                          ControlStyles.ResizeRedraw |
+                          ControlStyles.ContainerControl |
+                          ControlStyles.OptimizedDoubleBuffer |
+                          ControlStyles.SupportsTransparentBackColor
+                          , true);
+        }
+
+
+        [DllImport("user32.dll", CharSet = CharSet.Auto)]
+        public static extern int SendMessage(IntPtr hWnd, Int32 wMsg, bool wParam, Int32 lParam);
+
+        private const int WM_SetRedraw = 0XB;
+
+        public void SuspendDrawing()
+        {
+            SuspendLayout();
+            SendMessage(Handle, WM_SetRedraw, false, 0);
+        }
+
+        public void ResumeDrawing()
+        {
+            ResumeLayout(true);
+            SendMessage(Handle, WM_SetRedraw, true, 0);
+            Refresh();
+        }
+
+    }
+}
diff --git a/FrmCsvViewer.Designer.cs b/FrmCsvViewer.Designer.cs
index 50b6561..c01265e 100644
--- a/FrmCsvViewer.Designer.cs
+++ b/FrmCsvViewer.Designer.cs
@@ -37,8 +37,8 @@
             this.txtCurrentReg = new System.Windows.Forms.TextBox();
             this.txtTotalRegs = new System.Windows.Forms.TextBox();
             this.tblRegNumbers = new System.Windows.Forms.TableLayoutPanel();
-            this.pnlReg = new System.Windows.Forms.Panel();
-            this.pnlData = new System.Windows.Forms.Panel();
+            this.pnlReg = new CsvView.DoubleBufferPanel();
+            this.pnlData = new CsvView.DoubleBufferPanel();
             this.tblRegNumbers.SuspendLayout();
             this.pnlReg.SuspendLayout();
             this.SuspendLayout();
@@ -203,8 +203,8 @@
         private System.Windows.Forms.TextBox txtCurrentReg;
         private System.Windows.Forms.TextBox txtTotalRegs;
         private System.Windows.Forms.TableLayoutPanel tblRegNumbers;
-        private System.Windows.Forms.Panel pnlReg;
-        private System.Windows.Forms.Panel pnlData;
+        private CsvView.DoubleBufferPanel pnlReg;
+        private CsvView.DoubleBufferPanel pnlData;
     }
 }
 
diff --git a/FrmCsvViewer.cs b/FrmCsvViewer.cs
index a9d896d..148adf7 100644
--- a/FrmCsvViewer.cs
+++ b/FrmCsvViewer.cs
@@ -123,17 +123,17 @@ namespace CsvView
             return csvParser.Data[0];
         }
 
-        [DllImport("user32.dll", CharSet = CharSet.Auto)]
-        private static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, IntPtr lParam);
-
-        private const int WM_SetRedraw = 0XB;
-
+        bool _rendering = false;
         private void RenderReg(long currentReg)
         {
             if (_index == null || _index.Count <= 0)
             {
                 RenderRegClean();
             }
+
+            if (_rendering) { return; }
+            _rendering = true;
+
             pnlReg.Enabled = true;
             bool first = false;
             bool last = false;
@@ -148,6 +148,9 @@ namespace CsvView
                 last = true;
             }
 
+            pnlData.SuspendDrawing();
+
+            pnlData.Controls.Clear();
             _currentReg = currentReg;
             txtCurrentReg.Text = Convert.ToString(currentReg);
             txtTotalRegs.Text = Convert.ToString(_totalRegs);
@@ -158,9 +161,7 @@ namespace CsvView
             btnNextReg.Enabled = (last == false);
 
             List<string> currentData = Index_LoadReg((int)currentReg);
-            
-            pnlData.Visible = false;
-            pnlData.Controls.Clear();
+
             int y = 0;
             const int TexboxPadding = 5;
             const int Padding = 9;
@@ -171,7 +172,9 @@ namespace CsvView
                 pnlData.Controls.Add(txtValue);
                 y += txtValue.Height + Padding;
             }
-            pnlData.Visible = true;
+
+            pnlData.ResumeDrawing();
+            _rendering = false;
         }
 
         private TextBox RenderValue(string value, int y, int TexboxPadding, int Padding, int LineHeight)
@@ -199,12 +202,20 @@ namespace CsvView
 
         private void RenderRegClean()
         {
+            if (_rendering) { return; }
+            _rendering = true;
+
+            pnlData.SuspendDrawing();
+
+            pnlData.Controls.Clear();
             pnlReg.Enabled = false;
             txtCurrentReg.Text = string.Empty;
             txtTotalRegs.Text = string.Empty;
-            pnlData.Controls.Clear();
-        }
 
+            pnlData.ResumeDrawing();
+            _rendering = false;
+        }
+        
         private void btnFirstReg_Click(object sender, EventArgs e)
         {
             RenderReg(0);