diff --git a/imgui.h b/imgui.h
index 9662670..841506f 100644
--- a/imgui.h
+++ b/imgui.h
@@ -1630,11 +1630,11 @@
     IMGUI_API static char EmptyString[1];
 
     ImGuiTextBuffer()   { }
-    inline char         operator[](int i)       { IM_ASSERT(Buf.Data != NULL); return Buf.Data[i]; }
+    inline char         operator[](int i) const { IM_ASSERT(Buf.Data != NULL); return Buf.Data[i]; }
     const char*         begin() const           { return Buf.Data ? &Buf.front() : EmptyString; }
     const char*         end() const             { return Buf.Data ? &Buf.back() : EmptyString; }   // Buf is zero-terminated, so end() will point on the zero-terminator
     int                 size() const            { return Buf.Size ? Buf.Size - 1 : 0; }
-    bool                empty()                 { return Buf.Size <= 1; }
+    bool                empty() const           { return Buf.Size <= 1; }
     void                clear()                 { Buf.clear(); }
     void                reserve(int capacity)   { Buf.reserve(capacity); }
     const char*         c_str() const           { return Buf.Data ? Buf.Data : EmptyString; }
@@ -2111,7 +2111,7 @@
     IMGUI_API bool              Build();                    // Build pixels data. This is called automatically for you by the GetTexData*** functions.
     IMGUI_API void              GetTexDataAsAlpha8(unsigned char** out_pixels, int* out_width, int* out_height, int* out_bytes_per_pixel = NULL);  // 1 byte per-pixel
     IMGUI_API void              GetTexDataAsRGBA32(unsigned char** out_pixels, int* out_width, int* out_height, int* out_bytes_per_pixel = NULL);  // 4 bytes-per-pixel
-    bool                        IsBuilt()                   { return Fonts.Size > 0 && (TexPixelsAlpha8 != NULL || TexPixelsRGBA32 != NULL); }
+    bool                        IsBuilt() const             { return Fonts.Size > 0 && (TexPixelsAlpha8 != NULL || TexPixelsRGBA32 != NULL); }
     void                        SetTexID(ImTextureID id)    { TexID = id; }
 
     //-------------------------------------------
@@ -2144,7 +2144,7 @@
     const ImFontAtlasCustomRect*GetCustomRectByIndex(int index) const { if (index < 0) return NULL; return &CustomRects[index]; }
 
     // [Internal]
-    IMGUI_API void              CalcCustomRectUV(const ImFontAtlasCustomRect* rect, ImVec2* out_uv_min, ImVec2* out_uv_max);
+    IMGUI_API void              CalcCustomRectUV(const ImFontAtlasCustomRect* rect, ImVec2* out_uv_min, ImVec2* out_uv_max) const;
     IMGUI_API bool              GetMouseCursorTexData(ImGuiMouseCursor cursor, ImVec2* out_offset, ImVec2* out_size, ImVec2 out_uv_border[2], ImVec2 out_uv_fill[2]);
 
     //-------------------------------------------
diff --git a/imgui_draw.cpp b/imgui_draw.cpp
index 544e9f3..f73e0e3 100644
--- a/imgui_draw.cpp
+++ b/imgui_draw.cpp
@@ -1752,7 +1752,7 @@
     return CustomRects.Size - 1; // Return index
 }
 
-void ImFontAtlas::CalcCustomRectUV(const ImFontAtlasCustomRect* rect, ImVec2* out_uv_min, ImVec2* out_uv_max)
+void ImFontAtlas::CalcCustomRectUV(const ImFontAtlasCustomRect* rect, ImVec2* out_uv_min, ImVec2* out_uv_max) const
 {
     IM_ASSERT(TexWidth > 0 && TexHeight > 0);   // Font atlas needs to be built before we can calculate UV coordinates
     IM_ASSERT(rect->IsPacked());                // Make sure the rectangle has been packed
@@ -3201,9 +3201,9 @@
 {
     const unsigned long ADLER_MOD = 65521;
     unsigned long s1 = adler32 & 0xffff, s2 = adler32 >> 16;
-    unsigned long blocklen, i;
+    unsigned long blocklen = buflen % 5552;
 
-    blocklen = buflen % 5552;
+    unsigned long i;
     while (buflen) {
         for (i=0; i + 7 < blocklen; i += 8) {
             s1 += buffer[0], s2 += s1;
@@ -3230,10 +3230,9 @@
 
 static unsigned int stb_decompress(unsigned char *output, const unsigned char *i, unsigned int /*length*/)
 {
-    unsigned int olen;
     if (stb__in4(0) != 0x57bC0000) return 0;
     if (stb__in4(4) != 0)          return 0; // error! stream is > 4GB
-    olen = stb_decompress_length(i);
+    const unsigned int olen = stb_decompress_length(i);
     stb__barrier_in_b = i;
     stb__barrier_out_e = output + olen;
     stb__barrier_out_b = output;
diff --git a/imgui_internal.h b/imgui_internal.h
index 26660ba..3786b6f 100644
--- a/imgui_internal.h
+++ b/imgui_internal.h
@@ -624,7 +624,7 @@
     ImGuiMenuColumns();
     void        Update(int count, float spacing, bool clear);
     float       DeclColumns(float w0, float w1, float w2);
-    float       CalcExtraSpace(float avail_w);
+    float       CalcExtraSpace(float avail_w) const;
 };
 
 // Internal state of the currently focused/edited text input box
diff --git a/imgui_widgets.cpp b/imgui_widgets.cpp
index f31b013..1a82f29 100644
--- a/imgui_widgets.cpp
+++ b/imgui_widgets.cpp
@@ -5990,7 +5990,7 @@
     return ImMax(Width, NextWidth);
 }
 
-float ImGuiMenuColumns::CalcExtraSpace(float avail_w)
+float ImGuiMenuColumns::CalcExtraSpace(float avail_w) const
 {
     return ImMax(0.0f, avail_w - Width);
 }